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Bibliography on: Feathered Dinosaurs

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ESP: PubMed Auto Bibliography 18 Jun 2024 at 01:46 Created: 

Feathered Dinosaurs

"A feathered dinosaur is any species of dinosaur possessing feathers. For over 150 years, since scientific research began on dinosaurs in the early 1800s, dinosaurs were generally believed to be related to the reptile family; the word "dinosaur", coined in 1842 by paleontologist Richard Owen, comes from the Greek for "formidable lizard". This view began to shift during the so-called dinosaur renaissance in scientific research in the late 1960s, and by the mid-1990s significant evidence had emerged that dinosaurs are much more closely related to birds. In fact, birds are now believed to have descended directly from the theropod group of dinosaurs, and are thus classified as dinosaurs themselves, meaning that any modern bird can be considered a feathered dinosaur, since all modern birds possess feathers (with the exception of a few artificially selected chickens). Among extinct dinosaurs, feathers or feather-like integument have been discovered on dozens of genera via both direct and indirect fossil evidence. The vast majority of feather discoveries have been for coelurosaurian theropods. However, integument has also been discovered on at least three ornithischians, raising the likelihood that proto-feathers were also present in earlier dinosaurs." QUOTE FROM: Wikipedia

Created with PubMed® Query: ( (dinosaur OR dinosaurs) AND (feather OR feathers OR feathered OR plumage OR pigmentation OR pigment OR countershading) ) NOT pmcbook NOT ispreviousversion

Citations The Papers (from PubMed®)


RevDate: 2024-05-21
CmpDate: 2024-05-21

Yang Z, Jiang B, Xu J, et al (2024)

Cellular structure of dinosaur scales reveals retention of reptile-type skin during the evolutionary transition to feathers.

Nature communications, 15(1):4063.

Fossil feathers have transformed our understanding of integumentary evolution in vertebrates. The evolution of feathers is associated with novel skin ultrastructures, but the fossil record of these changes is poor and thus the critical transition from scaled to feathered skin is poorly understood. Here we shed light on this issue using preserved skin in the non-avian feathered dinosaur Psittacosaurus. Skin in the non-feathered, scaled torso is three-dimensionally replicated in silica and preserves epidermal layers, corneocytes and melanosomes. The morphology of the preserved stratum corneum is consistent with an original composition rich in corneous beta proteins, rather than (alpha-) keratins as in the feathered skin of birds. The stratum corneum is relatively thin in the ventral torso compared to extant quadrupedal reptiles, reflecting a reduced demand for mechanical protection in an elevated bipedal stance. The distribution of the melanosomes in the fossil skin is consistent with melanin-based colouration in extant crocodilians. Collectively, the fossil evidence supports partitioning of skin development in Psittacosaurus: a reptile-type condition in non-feathered regions and an avian-like condition in feathered regions. Retention of reptile-type skin in non-feathered regions would have ensured essential skin functions during the early, experimental stages of feather evolution.

RevDate: 2024-05-16
CmpDate: 2024-05-16

Chen CK, Chang YM, Jiang TX, et al (2024)

Conserved regulatory switches for the transition from natal down to juvenile feather in birds.

Nature communications, 15(1):4174.

The transition from natal downs for heat conservation to juvenile feathers for simple flight is a remarkable environmental adaptation process in avian evolution. However, the underlying epigenetic mechanism for this primary feather transition is mostly unknown. Here we conducted time-ordered gene co-expression network construction, epigenetic analysis, and functional perturbations in developing feather follicles to elucidate four downy-juvenile feather transition events. We report that extracellular matrix reorganization leads to peripheral pulp formation, which mediates epithelial-mesenchymal interactions for branching morphogenesis. α-SMA (ACTA2) compartmentalizes dermal papilla stem cells for feather renewal cycling. LEF1 works as a key hub of Wnt signaling to build rachis and converts radial downy to bilateral symmetry. Novel usage of scale keratins strengthens feather sheath with SOX14 as the epigenetic regulator. We show that this primary feather transition is largely conserved in chicken (precocial) and zebra finch (altricial) and discuss the possibility that this evolutionary adaptation process started in feathered dinosaurs.

RevDate: 2024-04-12

Chan YF, Lu CW, Kuo HC, et al (2024)

A chromosome-level genome assembly of the Asian house martin implies potential genes associated with the feathered-foot trait.

G3 (Bethesda, Md.) pii:7644378 [Epub ahead of print].

The presence of feathers is a vital characteristic among birds, yet most modern birds had no feather on their feet. The discoveries of feathers on the hind limbs of basal birds and dinosaurs have sparked an interest in the evolutionary origin and genetic mechanism of feathered feet. However, the majority of studies investigating the genes associated with this trait focused on domestic populations. Understanding the genetic mechanism underpinned feathered-foot development in wild birds is still in its infancy. Here, we assembled a chromosome-level genome of the Asian house martin (Delichon dasypus) using the long-read HiFi sequencing approach to initiate the search for genes associated with its feathered feet. We employed the whole genome alignment of D. dasypus with other swallow species to identify high-SNP regions and chromosomal inversions in the D. dasypus genome. After filtering out variations unrelated to D. dasypus evolution, we found six genes related to feather development near the high-SNP regions. We also detected three feather development genes in chromosomal inversions between the Asian house martin and the barn swallow genomes. We discussed their association with the WNT, BMP and FGF pathways and their potential roles in feathered-foot development. Future studies are encouraged to utilize the D. dasypus genome to explore the evolutionary process of the feathered-foot trait in avian species. This endeavor will shed light on the evolutionary path of feathers in birds.

RevDate: 2024-03-13
CmpDate: 2024-03-13

Xu X (2024)

Inferring aerial behavior in Mesozoic dinosaurs: Implications and uncertainties.

Proceedings of the National Academy of Sciences of the United States of America, 121(12):e2401482121.

RevDate: 2024-02-12

Kiat Y, JK O'Connor (2024)

Functional constraints on the number and shape of flight feathers.

Proceedings of the National Academy of Sciences of the United States of America, 121(8):e2306639121.

As a fundamental ecological aspect of most organisms, locomotor function significantly constrains morphology. At the same time, the evolution of novel locomotor abilities has produced dramatic morphological transformations, initiating some of the most significant diversifications in life history. Despite significant new fossil evidence, it remains unclear whether volant locomotion had a single or multiple origins in pennaraptoran dinosaurs and the volant abilities of individual taxa are controversial. The evolution of powered flight in modern birds involved exaptation of feathered surfaces extending off the limbs and tail yet most studies concerning flight potential in pennaraptorans do not account for the structure and morphology of the wing feathers themselves. Analysis of the number and shape of remex and rectrix feathers across a large dataset of extant birds indicates that the number of remiges and rectrices and the degree of primary vane asymmetry strongly correlate with locomotor ability revealing important functional constraints. Among these traits, phenotypic flexibility varies reflected by the different rates at which morphological changes evolve, such that some traits reflect the ancestral condition, whereas others reflect current locomotor function. While Mesozoic birds and Microraptor have remex morphologies consistent with extant volant birds, that of anchiornithines deviate significantly providing strong evidence this clade was not volant. The results of these analyses support a single origin of dinosaurian flight and indicate the early stages of feathered wing evolution are not sampled by the currently available fossil record.

RevDate: 2024-01-25

Park J, Son M, Park J, et al (2024)

Escape behaviors in prey and the evolution of pennaceous plumage in dinosaurs.

Scientific reports, 14(1):549.

Numerous non-avian dinosaurs possessed pennaceous feathers on their forelimbs (proto-wings) and tail. Their functions remain unclear. We propose that these pennaceous feathers were used in displays to flush hiding prey through stimulation of sensory-neural escape pathways in prey, allowing the dinosaurs to pursue the flushed prey. We evaluated the escape behavior of grasshoppers to hypothetical visual flush-displays by a robotic dinosaur, and we recorded neurophysiological responses of grasshoppers' escape pathway to computer animations of the hypothetical flush-displays by dinosaurs. We show that the prey of dinosaurs would have fled more often when proto-wings were present, especially distally and with contrasting patterns, and when caudal plumage, especially of a large area, was used during the hypothetical flush-displays. The reinforcing loop between flush and pursue functions could have contributed to the evolution of larger and stiffer feathers for faster running, maneuverability, and stronger flush-displays, promoting foraging based on the flush-pursue strategy. The flush-pursue hypothesis can explain the presence and distribution of the pennaceous feathers, plumage color contrasts, as well as a number of other features observed in early pennaraptorans. This scenario highlights that sensory-neural processes underlying prey's antipredatory reactions may contribute to the origin of major evolutionary innovations in predators.

RevDate: 2024-01-08

Dhouailly D (2024)

The avian ectodermal default competence to make feathers.

Developmental biology pii:S0012-1606(24)00002-2 [Epub ahead of print].

Feathers originate as protofeathers before birds, in pterosaurs and basal dinosaurs. What characterizes a feather is not only its outgrowth, but its barb cells differentiation and a set of beta-corneous proteins. Reticula appear concomitantly with feathers, as small bumps on plantar skin, made only of keratins. Avian scales, with their own set of beta-corneous proteins, appear more recently than feathers on the shank, and only in some species. In the chick embryo, when feather placodes form, all the non-feather areas of the integument are already specified. Among them, midventral apterium, cornea, reticula, and scale morphogenesis appear to be driven by negative regulatory mechanisms, which modulate the inherited capacity of the avian ectoderm to form feathers. Successive dermal/epidermal interactions, initiated by the Wnt/β-catenin pathway, and involving principally Eda/Edar, BMP, FGF20 and Shh signaling, are responsible for the formation not only of feather, but also of scale placodes and reticula, with notable differences in the level of Shh, and probably FGF20 expressions. This sequence is a dynamic and labile process, the turning point being the FGF20 expression by the placode. This epidermal signal endows its associated dermis with the memory to aggregate and to stimulate the morphogenesis that follows, involving even a re-initiation of the placode.

RevDate: 2023-10-27

Li WH, Chuong CM, Chen CK, et al (2023)

Transition from natal downs to juvenile feathers: conserved regulatory switches in Neoaves.

Research square

The transition from natal downs for heat conservation to juvenile feathers for simple flight is a remarkable environmental adaptation process in avian evolution. However, the underlying epigenetic mechanism for this primary feather transition is mostly unknown. Here we conducted time-ordered gene co-expression network construction, epigenetic analysis, and functional perturbations in developing feather follicles to elucidate four downy-juvenile feather transition events. We discovered that LEF1 works as a key hub of Wnt signaling to build rachis and converts radial downy to bilateral symmetry. Extracellular matrix reorganization leads to peripheral pulp formation, which mediates epithelial - mesenchymal interactions for branching morphogenesis. ACTA2 compartments dermal papilla stem cells for feather cycling. Novel usage of scale keratins strengthens feather sheath with SOX14 as the epigenetic regulator. We found this primary feather transition largely conserved in chicken (precocious) and zebra finch (altricial) and discussed the possibility that this evolutionary adaptation process started in feathered dinosaurs.

RevDate: 2023-09-22

Slater TS, Edwards NP, Webb SM, et al (2023)

Preservation of corneous β-proteins in Mesozoic feathers.

Nature ecology & evolution [Epub ahead of print].

Fossil proteins are valuable tools in evolutionary biology. Recent technological advances and better integration of experimental methods have confirmed the feasibility of biomolecular preservation in deep time, yielding new insights into the timing of key evolutionary transitions. Keratins (formerly α-keratins) and corneous β-proteins (CBPs, formerly β-keratins) are of particular interest as they define tissue structures that underpin fundamental physiological and ecological strategies and have the potential to inform on the molecular evolution of the vertebrate integument. Reports of CBPs in Mesozoic fossils, however, appear to conflict with experimental evidence for CBP degradation during fossilization. Further, the recent model for molecular modification of feather chemistry during the dinosaur-bird transition does not consider the relative preservation potential of different feather proteins. Here we use controlled taphonomic experiments coupled with infrared and sulfur X-ray spectroscopy to show that the dominant β-sheet structure of CBPs is progressively altered to α-helices with increasing temperature, suggesting that (α-)keratins and α-helices in fossil feathers are most likely artefacts of fossilization. Our analyses of fossil feathers shows that this process is independent of geological age, as even Cenozoic feathers can comprise primarily α-helices and disordered structures. Critically, our experiments show that feather CBPs can survive moderate thermal maturation. As predicted by our experiments, analyses of Mesozoic feathers confirm that evidence of feather CBPs can persist through deep time.

RevDate: 2023-07-29

Urban CA, Legendre LJ, JA Clarke (2023)

Description of natal down of the ostrich (Struthio camelus) and comparison with common quail (Coturnix coturnix): Developmental and evolutionary implications.

Journal of anatomy [Epub ahead of print].

Natal down is a feather stage that differs in both form and function from the definitive feathers of adult birds. It has a simpler structure that has been speculated to be similar to the body coverings of non-avian dinosaurs. However, inference of the evolution of natal down has been limited by our understanding of its structural variation in extant birds. Most descriptive work has focused on neognathous birds, limiting our knowledge of the full diversity of feathers in extant taxa. Here, we describe the natal down of a post-hatch ostrich (Struthio camelus) and compare it to that of a post-hatch quail (Coturnix coturnix). We confirm the presence of featherless spaces (apteria) in S. camelus and the lack of barbules on the tips of natal down in both species. We also find differences between dorsal and ventral natal down structures, such as barbule density in S. camelus and the extent of the bare portion of the barb in both species. Surprisingly, we do not find that the neoptiles of either species follow the ideal morphologies for increasing insulation. Finally, we hypothesize that the different barb types present in S. camelus natal down result from a large addition of new barb ridges during development, which is not known except in feathers with a rachis. These results have implications for our understanding of how structure informs function and development in understudied feather types, such as those shared by non-avian dinosaurs.

RevDate: 2023-07-06
CmpDate: 2023-07-05

Kiat Y, JK O'Connor (2023)

Rarity of molt evidence in early pennaraptoran dinosaurs suggests annual molt evolved later among Neornithes.

Communications biology, 6(1):687.

Feathers are a primitive trait among pennaraptoran dinosaurs, which today are represented by crown birds (Neornithes), the only clade of dinosaurs to survive the end Cretaceous mass extinction. Feathers are central to many important functions and therefore, maintaining plumage function is of great importance for survival. Thus, molt - by which new feathers are formed to replace old ones, is an essential process. Our limited knowledge regarding molt in early pennaraptoran evolution is based largely on a single Microraptor specimen. A survey of 92 feathered non-avian dinosaur and stem bird fossils did not find additional molting evidence. Due to its longer duration, in ornithological collections evidence of molt is found more frequently in extant bird species with sequential molts compared to those with more rapid simultaneous molts. The low frequency of molt occurrence among fossil specimens resembles collections of bird species with simultaneous molts. The dearth of molt evidence in the forelimbs of pennaraptoran specimens may have interesting implications regarding molt strategy during early avian evolution, and suggests that the yearly molting cycle may have evolved later, among crown birds.

RevDate: 2023-06-19
CmpDate: 2023-06-19

Sathe EA, Chronister NJ, R Dudley (2023)

Incipient wing flapping enhances aerial performance of a robotic paravian model.

Bioinspiration & biomimetics, 18(4):.

The functional origins of bird flight remain unresolved despite a diversity of hypothesized selective factors. Fossil taxa phylogenetically intermediate between typical theropod dinosaurs and modern birds exhibit dense aggregations of feathers on their forelimbs, and the evolving morphologies and kinematic activational patterns of these structures could have progressively enhanced aerodynamic force production over time. However, biomechanical functionality of flapping in such transitional structures is unknown. We evaluated a robot inspired by paravian morphology to model the effects of incremental increases in wing length, wingbeat frequency, and stroke amplitude on aerial performance. From a launch height of 2.8 m, wing elongation most strongly influenced distance travelled and time aloft for all frequency-amplitude combinations, although increased frequency and amplitude also enhanced performance. Furthermore, we found interaction effects among these three parameters such that when the wings were long, higher values of either wingbeat frequency or stroke amplitude synergistically improved performance. For launches from a height of 5.0 m, the effects of these flapping parameters appear to diminish such that only flapping at the highest frequency (5.7 Hz) and amplitude (60°) significantly increased performance. Our results suggest that a gliding animal at the physical scale relevant to bird flight origins, and with transitional wings, can improve aerodynamic performance via rudimentary wing flapping at relatively low frequencies and amplitudes. Such gains in horizontal translation and time aloft, as those found in this study, are likely to be advantageous for any taxon that engages in aerial behavior for purposes of transit or escape. This study thus demonstrates aerodynamic benefits of transition from a gliding stage to full-scale wing flapping in paravian taxa.

RevDate: 2023-04-28
CmpDate: 2023-04-28

Anonymous (2023)

Amber reveals beetles with a fluffy diet: dinosaur feathers.

Nature, 616(7958):632.

RevDate: 2023-05-09
CmpDate: 2023-04-19

Peñalver E, Peris D, Álvarez-Parra S, et al (2023)

Symbiosis between Cretaceous dinosaurs and feather-feeding beetles.

Proceedings of the National Academy of Sciences of the United States of America, 120(17):e2217872120.

Extant terrestrial vertebrates, including birds, have a panoply of symbiotic relationships with many insects and arachnids, such as parasitism or mutualism. Yet, identifying arthropod-vertebrate symbioses in the fossil record has been based largely on indirect evidence; findings of direct association between arthropod guests and dinosaur host remains are exceedingly scarce. Here, we present direct and indirect evidence demonstrating that beetle larvae fed on feathers from an undetermined theropod host (avian or nonavian) 105 million y ago. An exceptional amber assemblage is reported of larval molts (exuviae) intimately associated with plumulaceous feather and other remains, as well as three additional amber pieces preserving isolated conspecific exuviae. Samples were found in the roughly coeval Spanish amber deposits of El Soplao, San Just, and Peñacerrada I. Integration of the morphological, systematic, and taphonomic data shows that the beetle larval exuviae, belonging to three developmental stages, are most consistent with skin/hide beetles (family Dermestidae), an ecologically important group with extant keratophagous species that commonly inhabit bird and mammal nests. These findings show that a symbiotic relationship involving keratophagy comparable to that of beetles and birds in current ecosystems existed between their Early Cretaceous relatives.

RevDate: 2023-02-28

Uno Y, T Hirasawa (2023)

Origin of the propatagium in non-avian dinosaurs.

Zoological letters, 9(1):4.

Avian wings as organs for aerial locomotion are furnished with a highly specialized musculoskeletal system compared with the forelimbs of other tetrapod vertebrates. Among the specializations, the propatagium, which accompanies a skeletal muscle spanning between the shoulder and wrist on the leading edge of the wing, represents an evolutionary novelty established at a certain point in the lineage toward crown birds. However, because of the rarity of soft-tissue preservation in the fossil record, the evolutionary origin of the avian propatagium has remained elusive. Here we focus on articulated skeletons in the fossil record to show that angles of elbow joints in fossils are indicators of the propatagium in extant lineages of diapsids (crown birds and non-dinosaurian diapsids), and then use this relationship to narrow down the phylogenetic position acquiring the propatagium to the common ancestor of maniraptorans. Our analyses support the hypothesis that the preserved propatagium-like soft tissues in non-avian theropod dinosaurs (oviraptorosaurian Caudipteryx and dromaeosaurian Microraptor) are homologous with the avian propatagium, and indicate that all maniraptoran dinosaurs likely possessed the propatagium even before the origin of flight. On the other hand, the preserved angles of wrist joints in non-avian theropods are significantly greater than those in birds, suggesting that the avian interlocking wing-folding mechanism involving the ulna and radius had not fully evolved in non-avian theropods. Our study underscores that the avian wing was acquired through modifications of preexisting structures including the feather and propatagium.

RevDate: 2023-02-06
CmpDate: 2023-01-17

Padian K (2023)

25th anniversary of the first known feathered dinosaurs.

Nature, 613(7943):251-252.

RevDate: 2022-12-18
CmpDate: 2022-11-16

Pittman M, Kaye TG, Wang X, et al (2022)

Preserved soft anatomy confirms shoulder-powered upstroke of early theropod flyers, reveals enhanced early pygostylian upstroke, and explains early sternum loss.

Proceedings of the National Academy of Sciences of the United States of America, 119(47):e2205476119.

Anatomy of the first flying feathered dinosaurs, modern birds and crocodylians, proposes an ancestral flight system divided between shoulder and chest muscles, before the upstroke muscles migrated beneath the body. This ancestral flight system featured the dorsally positioned deltoids and supracoracoideus controlling the upstroke and the chest-bound pectoralis controlling the downstroke. Preserved soft anatomy is needed to contextualize the origin of the modern flight system, but this has remained elusive. Here we reveal the soft anatomy of the earliest theropod flyers preserved as residual skin chemistry covering the body and delimiting its margins. These data provide preserved soft anatomy that independently validate the ancestral theropod flight system. The heavily constructed shoulder and more weakly constructed chest in the early pygostylian Confuciusornis indicated by a preserved body profile, proposes the first upstroke-enhanced flight stroke. Slender ventral body profiles in the early-diverging birds Archaeopteryx and Anchiornis suggest habitual use of the pectoralis could not maintain the sternum through bone functional adaptations. Increased wing-assisted terrestrial locomotion potentially accelerated sternum loss through higher breathing requirements. Lower expected downstroke requirements in the early thermal soarer Sapeornis could have driven sternum loss through bone functional adaption, possibly encouraged by the higher breathing demands of a Confuciusornis-like upstroke. Both factors are supported by a slender ventral body profile. These data validate the ancestral shoulder/chest flight system and provide insights into novel upstroke-enhanced flight strokes and early sternum loss, filling important gaps in our understanding of the appearance of modern flight.

RevDate: 2022-07-16

Tahoun M, Engeser M, Namasivayam V, et al (2022)

Chemistry and Analysis of Organic Compounds in Dinosaurs.

Biology, 11(5):.

This review provides an overview of organic compounds detected in non-avian dinosaur fossils to date. This was enabled by the development of sensitive analytical techniques. Non-destructive methods and procedures restricted to the sample surface, e.g., light and electron microscopy, infrared (IR) and Raman spectroscopy, as well as more invasive approaches including liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), time-of-flight secondary ion mass spectrometry, and immunological methods were employed. Organic compounds detected in samples of dinosaur fossils include pigments (heme, biliverdin, protoporphyrin IX, melanin), and proteins, such as collagens and keratins. The origin and nature of the observed protein signals is, however, in some cases, controversially discussed. Molecular taphonomy approaches can support the development of suitable analytical methods to confirm reported findings and to identify further organic compounds in dinosaur and other fossils in the future. The chemical properties of the various organic compounds detected in dinosaurs, and the techniques utilized for the identification and analysis of each of the compounds will be discussed.

RevDate: 2022-05-03
CmpDate: 2022-04-25

Ortega RP (2022)

Pterosaurs were clad in colorful plumage.

Science (New York, N.Y.), 376(6591):335.

Study suggests feathers arose-and were used for display-well before reign of dinosaurs.

RevDate: 2022-05-31
CmpDate: 2022-04-27

Benton MJ (2022)

A colourful view of the origin of dinosaur feathers.

Nature, 604(7907):630-631.

RevDate: 2022-07-22
CmpDate: 2022-04-29

Cincotta A, Nicolaï M, Campos HBN, et al (2022)

Pterosaur melanosomes support signalling functions for early feathers.

Nature, 604(7907):684-688.

Remarkably well-preserved soft tissues in Mesozoic fossils have yielded substantial insights into the evolution of feathers[1]. New evidence of branched feathers in pterosaurs suggests that feathers originated in the avemetatarsalian ancestor of pterosaurs and dinosaurs in the Early Triassic[2], but the homology of these pterosaur structures with feathers is controversial[3,4]. Reports of pterosaur feathers with homogeneous ovoid melanosome geometries[2,5] suggest that they exhibited limited variation in colour, supporting hypotheses that early feathers functioned primarily in thermoregulation[6]. Here we report the presence of diverse melanosome geometries in the skin and simple and branched feathers of a tapejarid pterosaur from the Early Cretaceous found in Brazil. The melanosomes form distinct populations in different feather types and the skin, a feature previously known only in theropod dinosaurs, including birds. These tissue-specific melanosome geometries in pterosaurs indicate that manipulation of feather colour-and thus functions of feathers in visual communication-has deep evolutionary origins. These features show that genetic regulation of melanosome chemistry and shape[7-9] was active early in feather evolution.

RevDate: 2023-04-15

Chitimia-Dobler L, Mans BJ, Handschuh S, et al (2022)

A remarkable assemblage of ticks from mid-Cretaceous Burmese amber.

Parasitology, 149(6):1-36 [Epub ahead of print].

Four fossil ticks (Arachnida: Parasitiformes: Ixodida) are described from mid-Cretaceous (ca. 100 Ma) Burmese amber of Myanmar. Ixodes antiquorum sp. nov. (Ixodidae) is the first Mesozoic record of Ixodes and the oldest representative of the most species-rich extant tick genus. Its affinities appear to lie with modern Australian forms, consistent with the hypothesis that Burmese amber hosted Gondwanan faunal elements. Even more remarkable is Khimaira fossus gen. et sp. nov. which combines a body resembling that of a soft tick (Argasidae) with a basis capitulum more like that of a hard tick (Ixodidae). We refer it to Khimairidae fam. nov. as a possible transitional form between the two main families of ticks alive today. Another member of the extinct Deinocrotonidae is described as Deinocroton copia sp. nov., while the first described adult female for Cornupalpatum burmanicum is associated with a dinosaur feather barb.

RevDate: 2022-12-15
CmpDate: 2022-11-09

Akat E, Yenmiş M, Pombal MA, et al (2022)

Comparison of vertebrate skin structure at class level: A review.

Anatomical record (Hoboken, N.J. : 2007), 305(12):3543-3608.

The skin is a barrier between the internal and external environment of an organism. Depending on the species, it participates in multiple functions. The skin is the organ that holds the body together, covers and protects it, and provides communication with its environment. It is also the body's primary line of defense, especially for anamniotes. All vertebrates have multilayered skin composed of three main layers: the epidermis, the dermis, and the hypodermis. The vital mission of the integument in aquatic vertebrates is mucus secretion. Cornification began in apmhibians, improved in reptilians, and endured in avian and mammalian epidermis. The feather, the most ostentatious and functional structure of avian skin, evolved in the Mesozoic period. After the extinction of the dinosaurs, birds continued to diversify, followed by the enlargement, expansion, and diversification of mammals, which brings us to the most complicated skin organization of mammals with differing glands, cells, physiological pathways, and the evolution of hair. Throughout these radical changes, some features were preserved among classes such as basic dermal structure, pigment cell types, basic coloration genetics, and similar sensory features, which enable us to track the evolutionary path. The structural and physiological properties of the skin in all classes of vertebrates are presented. The purpose of this review is to go all the way back to the agnathans and follow the path step by step up to mammals to provide a comparative large and updated survey about vertebrate skin in terms of morphology, physiology, genetics, ecology, and immunology.

RevDate: 2022-06-10
CmpDate: 2022-05-03

Hendrickx C, Bell PR, Pittman M, et al (2022)

Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs.

Biological reviews of the Cambridge Philosophical Society, 97(3):960-1004.

Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in the group of theropod dinosaurs (Maniraptoriformes) that include crown Aves. Squamous or scaly reptilian-like skin is, however, considered the plesiomorphic condition for theropods and dinosaurs more broadly. Here, we review the morphology and distribution of non-feathered integumentary structures in non-avialan theropods, covering squamous skin and naked skin as well as dermal ossifications. The integumentary record of non-averostran theropods is limited to tracks, which ubiquitously show a covering of tiny reticulate scales on the plantar surface of the pes. This is consistent also with younger averostran body fossils, which confirm an arthral arrangement of the digital pads. Among averostrans, squamous skin is confirmed in Ceratosauria (Carnotaurus), Allosauroidea (Allosaurus, Concavenator, Lourinhanosaurus), Compsognathidae (Juravenator), and Tyrannosauroidea (Santanaraptor, Albertosaurus, Daspletosaurus, Gorgosaurus, Tarbosaurus, Tyrannosaurus), whereas dermal ossifications consisting of sagittate and mosaic osteoderms are restricted to Ceratosaurus. Naked, non-scale bearing skin is found in the contentious tetanuran Sciurumimus, ornithomimosaurians (Ornithomimus) and possibly tyrannosauroids (Santanaraptor), and also on the patagia of scansoriopterygids (Ambopteryx, Yi). Scales are surprisingly conservative among non-avialan theropods compared to some dinosaurian groups (e.g. hadrosaurids); however, the limited preservation of tegument on most specimens hinders further interrogation. Scale patterns vary among and/or within body regions in Carnotaurus, Concavenator and Juravenator, and include polarised, snake-like ventral scales on the tail of the latter two genera. Unusual but more uniformly distributed patterning also occurs in Tyrannosaurus, whereas feature scales are present only in Albertosaurus and Carnotaurus. Few theropods currently show compelling evidence for the co-occurrence of scales and feathers (e.g. Juravenator, Sinornithosaurus), although reticulate scales were probably retained on the mani and pedes of many theropods with a heavy plumage. Feathers and filamentous structures appear to have replaced widespread scaly integuments in maniraptorans. Theropod skin, and that of dinosaurs more broadly, remains a virtually untapped area of study and the appropriation of commonly used techniques in other palaeontological fields to the study of skin holds great promise for future insights into the biology, taphonomy and relationships of these extinct animals.

RevDate: 2021-12-14
CmpDate: 2021-12-14

Álvarez-Parra S, Pérez-de la Fuente R, Peñalver E, et al (2021)

Dinosaur bonebed amber from an original swamp forest soil.

eLife, 10:.

Dinosaur bonebeds with amber content, yet scarce, offer a superior wealth and quality of data on ancient terrestrial ecosystems. However, the preserved palaeodiversity and/or taphonomic characteristics of these exceptional localities had hitherto limited their palaeobiological potential. Here, we describe the amber from the Lower Cretaceous dinosaur bonebed of Ariño (Teruel, Spain) using a multidisciplinary approach. Amber is found in both a root layer with amber strictly in situ and a litter layer mainly composed of aerial pieces unusually rich in bioinclusions, encompassing 11 insect orders, arachnids, and a few plant and vertebrate remains, including a feather. Additional palaeontological data-charophytes, palynomorphs, ostracods- are provided. Ariño arguably represents the most prolific and palaeobiologically diverse locality in which fossiliferous amber and a dinosaur bonebed have been found in association, and the only one known where the vast majority of the palaeontological assemblage suffered no or low-grade pre-burial transport. This has unlocked unprecedentedly complete and reliable palaeoecological data out of two complementary windows of preservation-the bonebed and the amber-from the same site.

RevDate: 2022-04-08
CmpDate: 2022-04-08

Benton MJ, Currie PJ, X Xu (2021)

A thing with feathers.

Current biology : CB, 31(21):R1406-R1409.

Michael Benton and colleagues reminisce about the discovery of Sinosauripteryx, the first feathered dinosaur.

RevDate: 2022-03-04
CmpDate: 2022-03-04

Davis SN, JA Clarke (2022)

Estimating the distribution of carotenoid coloration in skin and integumentary structures of birds and extinct dinosaurs.

Evolution; international journal of organic evolution, 76(1):42-57.

Carotenoids are pigments responsible for most bright yellow, red, and orange hues in birds. Their distribution has been investigated in avian plumage, but the evolution of their expression in skin and other integumentary structures has not been approached in detail. Here, we investigate the expression of carotenoid-consistent coloration across tissue types in all extant, nonpasserine species (n = 4022) and archelosaur outgroups in a phylogenetic framework. We collect dietary data for a subset of birds and investigate how dietary carotenoid intake may relate to carotenoid expression in various tissues. We find that carotenoid-consistent expression in skin or nonplumage keratin has a 50% probability of being present in the most recent common ancestor of Archosauria. Skin expression has a similar probability at the base of the avian crown clade, but plumage expression is unambiguously absent in that ancestor and shows hundreds of independent gains within nonpasserine neognaths, consistent with previous studies. Although our data do not support a strict sequence of tissue expression in nonpasserine birds, we find support that expression of carotenoid-consistent color in nonplumage integument structures might evolve in a correlated manner and feathers are rarely the only region of expression. Taxa with diets high in carotenoid content also show expression in more body regions and tissue types. Our results may inform targeted assays for carotenoids in tissues other than feathers, and expectations of these pigments in nonavian dinosaurs. In extinct groups, bare-skin regions and the rhamphotheca, especially in species with diets rich in plants, may express these pigments, which are not expected in feathers or feather homologues.

RevDate: 2021-12-14
CmpDate: 2021-12-10

Pittman M, Barlow LA, Kaye TG, et al (2021)

Pterosaurs evolved a muscular wing-body junction providing multifaceted flight performance benefits: Advanced aerodynamic smoothing, sophisticated wing root control, and wing force generation.

Proceedings of the National Academy of Sciences of the United States of America, 118(44):.

Pterosaurs were the first vertebrate flyers and lived for over 160 million years. However, aspects of their flight anatomy and flight performance remain unclear. Using laser-stimulated fluorescence, we observed direct soft tissue evidence of a wing root fairing in a pterosaur, a feature that smooths out the wing-body junction, reducing associated drag, as in modern aircraft and flying animals. Unlike bats and birds, the pterosaur wing root fairing was unique in being primarily made of muscle rather than fur or feathers. As a muscular feature, pterosaurs appear to have used their fairing to access further flight performance benefits through sophisticated control of their wing root and contributions to wing elevation and/or anterior wing motion during the flight stroke. This study underscores the value of using new instrumentation to fill knowledge gaps in pterosaur flight anatomy and evolution.

RevDate: 2022-04-08
CmpDate: 2022-04-08

Wang M, O'Connor JK, Zhao T, et al (2021)

An Early Cretaceous enantiornithine bird with a pintail.

Current biology : CB, 31(21):4845-4852.e2.

Enantiornithes are the most successful group of Mesozoic birds, arguably representing the first global avian radiation,[1-4] and commonly resolved as the sister to the Ornithuromorpha, the clade within which all living birds are nested.[1][,][3] The wealth of fossils makes it feasible to comparatively test evolutionary hypotheses about the pattern and mode of eco-morphological diversity of these sister clades that co-existed for approximately 65 Ma. Here, we report a new Early Cretaceous enantiornithine, Yuanchuavis kompsosoura gen. et. sp. nov., with a rectricial fan combined with an elongate central pair of fully pennaceous rachis-dominated plumes, constituting a new tail plumage previously unknown among nonavialan dinosaurs and Mesozoic birds but which strongly resembles the pintail in many neornithines. The extravagant but aerodynamically costly long central plumes, as an honest signal of quality, likely evolved in enantiornithines through the handicap process of sexual selection. The contrasting tail morphotypes observed between enantiornithines and early ornithuromorphs reflect the complex interplay between sexual and natural selections and indicate that each lineage experienced unique pressures reflecting ecological differences. As in neornithines, early avialans repeatedly evolved extravagant structures highlighting the importance of sexual selection in shaping the plumage of feathered dinosaurs, even early in their evolutionary history.

RevDate: 2023-02-03
CmpDate: 2021-07-19

Wang M, Stidham TA, Li Z, et al (2021)

Cretaceous bird with dinosaur skull sheds light on avian cranial evolution.

Nature communications, 12(1):3890.

The transformation of the bird skull from an ancestral akinetic, heavy, and toothed dinosaurian morphology to a highly derived, lightweight, edentulous, and kinetic skull is an innovation as significant as powered flight and feathers. Our understanding of evolutionary assembly of the modern form and function of avian cranium has been impeded by the rarity of early bird fossils with well-preserved skulls. Here, we describe a new enantiornithine bird from the Early Cretaceous of China that preserves a nearly complete skull including the palatal elements, exposing the components of cranial kinesis. Our three-dimensional reconstruction of the entire enantiornithine skull demonstrates that this bird has an akinetic skull indicated by the unexpected retention of the plesiomorphic dinosaurian palate and diapsid temporal configurations, capped with a derived avialan rostrum and cranial roof, highlighting the highly modular and mosaic evolution of the avialan skull.

RevDate: 2021-10-08
CmpDate: 2021-10-08

Pittman M, Habib MB, Dececchi TA, et al (2021)

Response to Serrano and Chiappe.

Current biology : CB, 31(8):R372-R373.

In the recent study in Current Biology by Pei and colleagues[1], we used two proxies - wing loading and specific lift - to reconstruct powered flight potential across the vaned feathered fossil pennaraptorans. The results recovered multiple origins of powered flight. We respectfully disagree with the criticism raised by Serrano and Chiappe[2] that wing loading and specific lift, used in sequence, fail to discriminate between powered flight and gliding. We will explain this in reference to our original conservative approach.

RevDate: 2021-10-08
CmpDate: 2021-10-08

Serrano FJ, LM Chiappe (2021)

Independent origins of powered flight in paravian dinosaurs?.

Current biology : CB, 31(8):R370-R372.

Feathered dinosaurs discovered during the last decades have illuminated the transition from land to air in these animals, underscoring a significant degree of experimentation in wing-assisted locomotion around the origin of birds. Such evolutionary experimentation led to lineages achieving either wing-assisted running, four-winged gliding, or membrane-winged gliding. Birds are widely accepted as the only dinosaur lineage that achieved powered flight, a key innovation for their evolutionary success. However, in a recent paper in Current Biology, Pei and colleagues[1] disputed this view. They concluded that three other lineages of paravian dinosaurs (those more closely related to birds than to oviraptorosaurs) - Unenlagiinae, Microraptorinae and Anchiornithinae - could have evolved powered flight independently. While we praise the detailed phylogenetic framework of Pei and colleagues[1] and welcome a new attempt to understand the onset of flight in dinosaurs, we here expose a set of arguments that significantly weaken their evidence supporting a multiple origin of powered flight. Specifically, we maintain that the two proxies used by Pei and colleagues[1] to assess powered flight potential in non-avian paravians - wing loading and specific lift - fail to discriminate between powered flight (thrust generated by flapping) and passive flight (gliding).

RevDate: 2021-03-22
CmpDate: 2021-03-10

Grimaldi DA, IM Vea (2021)

Insects with 100 million-year-old dinosaur feathers are not ectoparasites.

Nature communications, 12(1):1469.

RevDate: 2022-01-21
CmpDate: 2022-01-21

Vinther J, Nicholls R, DA Kelly (2021)

A cloacal opening in a non-avian dinosaur.

Current biology : CB, 31(4):R182-R183.

The Frankfurt specimen of Psittacosaurus sp. (SMF R 4970) from the Early Cretaceous Jehol deposits of Liaoning (Figure S1) exhibits exceptional preservation of scale-clad integument[1]. Preservation of colour patterns and countershading allowed a detailed reconstruction of this individual's physical appearance. It was previously noted that the cloacal region was preserved[2], but its detailed anatomy was incorrectly reconstructed. We show here that the fine anatomy of the vent is remarkably well preserved and can be retrodeformed to illustrate its three-dimensional nature. The vent's scale anatomy and pigmentation are distinct from adjacent body regions, and although its anatomy does not reveal much information about the ecology, or sex, of this dinosaur, it suggests possible roles for visual and olfactory signalling.

RevDate: 2022-01-28
CmpDate: 2021-06-29

Kaye TG, Pittman M, WR Wahl (2020)

Archaeopteryx feather sheaths reveal sequential center-out flight-related molting strategy.

Communications biology, 3(1):745.

Modern flying birds molt to replace old and worn feathers that inhibit flight performance, but its origins are unclear. We address this by presenting and evaluating a ~150 million year old record of molting in a feathered dinosaur from the early bird Archaeopteryx. Laser-Stimulated Fluorescence revealed feather sheaths that are otherwise invisible under white light. These are separated by one feather and are not in numerical sequential order and are mirrored in both wings. This indicates that a sequential center-out molting strategy was already present at the origins of flight, which is used in living falcons to preserve maximum flight performance. This strategy would have been a welcome advantage for early theropod flyers that had poor flight capabilities. This discovery provides important insights into how birds refined their early flight capabilities before the appearance of the keeled sternum, pygostyle and triosseal canal.

RevDate: 2021-08-30
CmpDate: 2021-08-30

Ksepka DT (2020)

Feathered dinosaurs.

Current biology : CB, 30(22):R1347-R1353.

Feathers are the most complex integumentary structures in the animal world. They come in a variety of forms, the most familiar of which are remiges (flight feathers). Flight feathers are composed of a central shaft made up of a hollow calamus (quill), which is inserted into the skin, and a more distal rachis. Hundreds of parallel barbs branch from the sides of the rachis. In turn, smaller hooked barbules branch off the barbs, allowing them to interlock in a tight zipper-like fashion to form vanes. Variations in rachis, barb and barbule morphology result in other feather types such as contour feathers, bristles and down feathers. Feathers have a remarkable array of functions - they form airfoils and elaborate display structures, they serve to camouflage and insulate, to generate and help detect sound, and even to disintegrate into powder to condition other feathers.

RevDate: 2020-11-23
CmpDate: 2020-11-23

Álvarez-Parra S, Delclòs X, Solórzano-Kraemer MM, et al (2020)

Cretaceous amniote integuments recorded through a taphonomic process unique to resins.

Scientific reports, 10(1):19840.

Fossil records of vertebrate integuments are relatively common in both rocks, as compressions, and amber, as inclusions. The integument remains, mainly the Mesozoic ones, are of great interest due to the panoply of palaeobiological information they can provide. We describe two Spanish Cretaceous amber pieces that are of taphonomic importance, one bearing avian dinosaur feather remains and the other, mammalian hair. The preserved feather remains originated from an avian dinosaur resting in contact with a stalactite-shaped resin emission for the time it took for the fresh resin to harden. The second piece shows three hair strands recorded on a surface of desiccation, with the characteristic scale pattern exceptionally well preserved and the strands aligned together, which can be considered the record of a tuft. These assemblages were recorded through a rare biostratinomic process we call "pull off vestiture" that is different from the typical resin entrapment and embedding of organisms and biological remains, and unique to resins. The peculiarity of this process is supported by actualistic observations using sticky traps in Madagascar. Lastly, we reinterpret some exceptional records from the literature in the light of that process, thus bringing new insight to the taphonomic and palaeoecological understanding of the circumstances of their origins.

RevDate: 2021-09-30
CmpDate: 2020-10-29

Carney RM, Tischlinger H, MD Shawkey (2020)

Evidence corroborates identity of isolated fossil feather as a wing covert of Archaeopteryx.

Scientific reports, 10(1):15593.

The historic fossil feather from the Jurassic Solnhofen has played a pivotal but controversial role in our evolutionary understanding of dinosaurs and birds. Recently, a study confirmed the diagnostic morphology of the feather's original calamus, but nonetheless challenged the proposed identity as an Archaeopteryx covert. However, there are errors in the results and interpretations presented. Here we show that the feather is most likely an upper major primary covert, based on its long calamus (23.3% total length) and eight other anatomical attributes. Critically, this hypothesis is independently supported by evidence of similar primary coverts in multiple specimens of Archaeopteryx-including from the same fossil site and horizon as the isolated feather. We also provide additional insights, such as an updated colour reconstruction of the entire feather as matte black, with 90% probability. Given the isolated nature of the fossil feather, we can never know the anatomical and taxonomic provenance with 100% certainty. However, based on all available evidence, the most empirical and parsimonious conclusion is that this feather represents a primary covert from the ancient wing of Archaeopteryx.

RevDate: 2021-05-19
CmpDate: 2021-01-11

Yang Z, Jiang B, McNamara ME, et al (2020)

Reply to: No protofeathers on pterosaurs.

Nature ecology & evolution, 4(12):1592-1593.

RevDate: 2021-05-19
CmpDate: 2021-01-11

Unwin DM, DM Martill (2020)

No protofeathers on pterosaurs.

Nature ecology & evolution, 4(12):1590-1591.

RevDate: 2022-11-02
CmpDate: 2021-05-25

Klingler JJ (2020)

The evolution of the pectoral extrinsic appendicular and infrahyoid musculature in theropods and its functional and behavioral importance.

Journal of anatomy, 237(5):870-889.

Birds have lost and modified the musculature joining the pectoral girdle to the skull and hyoid, called the pectoral extrinsic appendicular and infrahyoid musculature. These muscles include the levator scapulae, sternomandibularis, sternohyoideus, episternocleidomastoideus, trapezius, and omohyoideus. As non-avian theropod dinosaurs are the closest relatives to birds, it is worth investigating what conditions they may have exhibited to learn when and how these muscles were lost or modified. Using extant phylogenetic bracketing, osteological correlates and non-osteological influences of these muscles are identified and discussed. Compsognathids and basal Maniraptoriformes were found to have been the likeliest transition points of a derived avian condition of losing or modifying these muscles. Increasing needs to control the feather tracts of the neck and shoulder, for insulation, display, or tightening/readjustment of the skin after dynamic neck movements may have been the selective force that drove some of these muscles to be modified into dermo-osseous muscles. The loss and modification of shoulder protractors created a more immobile girdle that would later be advantageous for flight in birds. The loss of the infrahyoid muscles freed the hyolarynx, trachea, and esophagus which may have aided in vocal tract filtering.

RevDate: 2021-10-07
CmpDate: 2021-08-12

Pei R, Pittman M, Goloboff PA, et al (2020)

Potential for Powered Flight Neared by Most Close Avialan Relatives, but Few Crossed Its Thresholds.

Current biology : CB, 30(20):4033-4046.e8.

Uncertainties in the phylogeny of birds (Avialae) and their closest relatives have impeded deeper understanding of early theropod flight. To help address this, we produced an updated evolutionary hypothesis through an automated analysis of the Theropod Working Group (TWiG) coelurosaurian phylogenetic data matrix. Our larger, more resolved, and better-evaluated TWiG-based hypothesis supports the grouping of dromaeosaurids + troodontids (Deinonychosauria) as the sister taxon to birds (Paraves) and the recovery of Anchiornithinae as the earliest diverging birds. Although the phylogeny will continue developing, our current results provide a pertinent opportunity to evaluate what we know about early theropod flight. With our results and available data for vaned feathered pennaraptorans, we estimate the potential for powered flight among early birds and their closest relatives. We did this by using an ancestral state reconstruction analysis calculating maximum and minimum estimates of two proxies of powered flight potential-wing loading and specific lift. These results confirm powered flight potential in early birds but its rarity among the ancestors of the closest avialan relatives (select unenlagiine and microraptorine dromaeosaurids). For the first time, we find a broad range of these ancestors neared the wing loading and specific lift thresholds indicative of powered flight potential. This suggests there was greater experimentation with wing-assisted locomotion before theropod flight evolved than previously appreciated. This study adds invaluable support for multiple origins of powered flight potential in theropods (≥3 times), which we now know was from ancestors already nearing associated thresholds, and provides a framework for its further study. VIDEO ABSTRACT.

RevDate: 2021-08-09
CmpDate: 2021-08-09

Kiat Y, Balaban A, Sapir N, et al (2020)

Sequential Molt in a Feathered Dinosaur and Implications for Early Paravian Ecology and Locomotion.

Current biology : CB, 30(18):3633-3638.e2.

Feather molt is an important life-history process in birds, but little is known about its evolutionary history. Here, we report on the first fossilized evidence of sequential wing feather molt, a common strategy among extant birds, identified in the Early Cretaceous four-winged dromaeosaurid Microraptor. Analysis of wing feather molt patterns and ecological properties in extant birds imply that Microraptor maintained its flight ability throughout the entire annual cycle, including the molt period. Therefore, we conclude that flight was essential for either its daily foraging or escaping from predators. Our findings propose that the development of sequential molt is the outcome of evolutionary forces to maintain flight capability throughout the entire annual cycle in both extant birds and non-avialan paravian dinosaurs from 120 mya. VIDEO ABSTRACT.

RevDate: 2021-04-09
CmpDate: 2021-04-09

Jagadeesan Y, Meenakshisundaram S, Saravanan V, et al (2020)

Sustainable production, biochemical and molecular characterization of thermo-and-solvent stable alkaline serine keratinase from novel Bacillus pumilus AR57 for promising poultry solid waste management.

International journal of biological macromolecules, 163:135-146.

The increasing amount of recalcitrant keratinous wastes generated from the poultry industry poses a serious threat to the environment. Keratinase have gained much attention to convert these wastes into valuable products. Ever since primitive feathers first appeared on dinosaurs, microorganisms have evolved to degrade this most recalcitrant keratin. In this study, we identified a promising keratinolytic bacterial strain for bioconversion of poultry solid wastes. A true keratinolytic bacterium was isolated from the slaughterhouse soil and was identified and designated as Bacillus pumilus AR57 by 16S rRNA sequencing. For enhanced keratinase production and rapid keratin degradation, the media components and substrate concentration were optimized through shake flask culture. White chicken feather (1% w/v) was found to be the good substrate concentration for high keratinase production when supplemented with simple medium ingredients. The biochemical characterization reveals astounding results which makes the B. pumilus AR57 keratinase as a novel and unique protease. Optimum activity of the crude enzyme was exhibited at pH 9 and 45 °C. The crude extracellular keratinase was characterized as thermo-and-solvent (DMSO) stable serine keratinase. Bacillus pumilus AR57 showed complete degradation (100%) of white chicken feather (1% w/v) within 18 h when incubated in modified minimal medium supplemented with DMSO (1% v/v) at 150 rpm at 37 °C. Keratinase from modified minimal medium supplemented with DMSO exhibits a half-life of 4 days. Whereas, keratinase from the modified minimal medium fortified with white chicken feather (1% w/v) was stable for 3 h only. Feather meal produced by B. pumilus AR57 was found to be rich in essential amino acids. Hence, we proposed B. pumilus AR57 as a potential candidate for the future application in eco-friendly bioconversion of poultry waste and the keratinase could play a pivotal role in the detergent industry. While feather meal may serve as an alternative to produce animal feed and biofertilizers.

RevDate: 2022-07-20
CmpDate: 2021-07-23

Wang S, Chang WL, Zhang Q, et al (2020)

Variations of Mesozoic feathers: Insights from the morphogenesis of extant feather rachises.

Evolution; international journal of organic evolution, 74(9):2121-2133.

The rachises of extant feathers, composed of dense cortex and spongy internal medulla, are flexible and light, yet stiff enough to withstand the load required for flight, among other functions. Incomplete knowledge of early feathers prevents a full understanding of how cylindrical rachises have evolved. Bizarre feathers with unusually wide and flattened rachises, known as "rachis-dominated feathers" (RDFs), have been observed in fossil nonavian and avian theropods. Newly discovered RDFs embedded in early Late Cretaceous Burmese ambers (about 99 million year ago) suggest the unusually wide and flattened rachises mainly consist of a dorsal cortex, lacking a medulla and a ventral cortex. Coupled with findings on extant feather morphogenesis, known fossil RDFs were categorized into three morphotypes based on their rachidial configurations. For each morphotype, potential developmental scenarios were depicted by referring to the rachidial development in chickens, and relative stiffness of each morphotype was estimated through functional simulations. The results suggest rachises of RDFs are developmentally equivalent to a variety of immature stages of cylindrical rachises. Similar rachidial morphotypes documented in extant penguins suggest that the RDFs are not unique to Mesozoic theropods, although they are likely to have evolved independently in extant penguins.

RevDate: 2021-03-26
CmpDate: 2020-11-25

Jasinski SE, Sullivan RM, P Dodson (2020)

New Dromaeosaurid Dinosaur (Theropoda, Dromaeosauridae) from New Mexico and Biodiversity of Dromaeosaurids at the end of the Cretaceous.

Scientific reports, 10(1):5105.

Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the time of their extinction near the Cretaceous-Paleogene boundary. Here we report on a new dromaeosaurid, Dineobellator notohesperus, gen. and sp. nov., consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, the first diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southern United States (southern Laramidia). The holotype includes elements of the skull, axial, and appendicular skeleton. The specimen reveals a host of morphologies that shed light on new behavioral attributes for these feathered dinosaurs. Unique features on its forelimbs suggest greater strength capabilities in flexion than the normal dromaeosaurid condition, in conjunction with a relatively tighter grip strength in the manual claws. Aspects of the caudal vertebrae suggest greater movement near the tail base, aiding in agility and predation. Phylogenetic analysis places Dineobellator within Velociraptorinae. Its phylogenetic position, along with that of other Maastrichtian taxa (Acheroraptor and Dakotaraptor), suggests dromaeosaurids were still diversifying at the end of the Cretaceous. Furthermore, its recovery as a second North American Maastrichtian velociraptorine suggests vicariance of North American velociraptorines after a dispersal event during the Campanian-Maastrichtian from Asia. Features of Dineobellator also imply that dromaeosaurids were active predators that occupied discrete ecological niches while living in the shadow of Tyrannosaurus rex, until the end of the dinosaurs' reign.

RevDate: 2022-07-16
CmpDate: 2021-04-02

Voegele KK, Ullmann PV, Lamanna MC, et al (2020)

Appendicular myological reconstruction of the forelimb of the giant titanosaurian sauropod dinosaur Dreadnoughtus schrani.

Journal of anatomy, 237(1):133-154.

Soft tissues are variably preserved in the fossil record with external tissues, such as skin and feathers, more frequently preserved than internal tissues (e.g. muscles). More commonly, soft tissues leave traces of their locations on bones and, for muscles, these clues can be used to reconstruct the musculature of extinct vertebrates, thereby enhancing our understanding of how these organisms moved and the evolution of their locomotor patterns. Herein we reconstruct the forelimb and shoulder girdle musculature of the giant titanosaurian sauropod Dreadnoughtus schrani based on observations of osteological correlates and dissections of taxa comprising the Extant Phylogenetic Bracket of non-avian dinosaurs (crocodilians and birds). Fossils of Dreadnoughtus exhibit remarkably well-preserved, well-developed, and extensive muscle scars. Furthermore, this taxon is significantly larger-bodied than any titanosaurian for which a myological reconstruction has previously been attempted, rendering this myological study highly informative for the clade. In total, 28 muscles were investigated in this study, for which 46 osteological correlates were identified; these osteological correlates allowed the reconstruction of 16 muscles on the basis of Level I or Level II inferences (i.e. not Level I' or Level II' inferences). Comparisons with other titanosaurians suggest widespread myological variation in the clade, although potential phylogenetic patterns are often obscured by fragmentary preservation, infrequent myological studies, and lack of consensus on the systematic position of many taxa. By identifying myological variations within the clade, we can begin to address specific evolutionary and biomechanical questions related to the locomotor evolution in these sauropods.

RevDate: 2021-02-08
CmpDate: 2021-02-08

Poust AW, Gao C, Varricchio DJ, et al (2020)

A new microraptorine theropod from the Jehol Biota and growth in early dromaeosaurids.

Anatomical record (Hoboken, N.J. : 2007), 303(4):963-987.

Fossils from the Jehol Group (Early Cretaceous, Liaoning Province, China) are integral to our understanding of Paraves, the clade of dinosaurs grouping dromaeosaurids, troodontids, and avialians, including living birds. However, many taxa are represented by specimens of unclear ontogenetic age. Without a more thorough understanding of ontogeny, evolutionary relationships and significance of character states within paravian dinosaurs may be obscured and our ability to infer their biology restricted. We describe a complete specimen of a new microraptorine dromaeosaur, Wulong bohaiensis gen. et sp. nov., from the geologically young Jiufotang Formation (Aptian) that helps solve this problem. Phylogenetic analysis recovers the specimen within a monophyletic Microraptorinae. Preserved in articulation on a single slab, the type specimen is small and exhibits osteological markers of immaturity identified in other archosaurs, such as bone texture and lack of fusion. To contextualize this signal, we histologically sampled the tibia, fibula, and humerus and compared them with new samples from the closely related and osteologically mature Sinornithosaurus. Histology shows both specimens to be young and still growing at death, indicating an age for the new dinosaur of about 1 year. The holotype possesses several feather types, including filamentous feathers, pennaceous primaries, and long rectrices, establishing that their growth preceded skeletal maturity and full adult size in some dromaeosaurids. Comparison of histology in the new taxon and Sinornithosaurus indicates that macroscopic signs of maturity developed after the first year, but before cessation of growth, demonstrating that nonhistological indicators of adulthood may be misleading when applied to dromaeosaurids. Anat Rec, 303:963-987, 2020. © 2020 American Association for Anatomy.

RevDate: 2020-09-17
CmpDate: 2020-09-17

Rezende EL, Bacigalupe LD, Nespolo RF, et al (2020)

Shrinking dinosaurs and the evolution of endothermy in birds.

Science advances, 6(1):eaaw4486.

The evolution of endothermy represents a major transition in vertebrate history, yet how and why endothermy evolved in birds and mammals remains controversial. Here, we combine a heat transfer model with theropod body size data to reconstruct the evolution of metabolic rates along the bird stem lineage. Results suggest that a reduction in size constitutes the path of least resistance for endothermy to evolve, maximizing thermal niche expansion while obviating the costs of elevated energy requirements. In this scenario, metabolism would have increased with the miniaturization observed in the Early-Middle Jurassic (~180 to 170 million years ago), resulting in a gradient of metabolic levels in the theropod phylogeny. Whereas basal theropods would exhibit lower metabolic rates, more recent nonavian lineages were likely decent thermoregulators with elevated metabolism. These analyses provide a tentative temporal sequence of the key evolutionary transitions that resulted in the emergence of small, endothermic, feathered flying dinosaurs.

RevDate: 2021-02-08
CmpDate: 2021-02-08

Chiappe LM, Di L, Serrano FJ, et al (2020)

Anatomy and Flight Performance of the Early Enantiornithine Bird Protopteryx fengningensis: Information from New Specimens of the Early Cretaceous Huajiying Formation of China.

Anatomical record (Hoboken, N.J. : 2007), 303(4):716-731.

The Early Cretaceous (∼131 Million Years Ago) Protopteryx fengningensis is one of the oldest and most primitive enantiornithine birds; however, knowledge of its anatomy has largely been limited to the succinct description of two specimens (holotype and paratype). This study describes two new specimens of P. fengningensis preserving most of the skeleton and plumage, and it therefore adds significantly to understanding the morphology of this important species and the character evolution of enantiornithine birds. The well-preserved plumage of these specimens also affords a quantitative assessment of the flight performance of P. fengningensis. Our aerodynamic considerations indicate that this early enantiornithine was capable of intermittent flight (bounding or flap-gliding), thus marking the earliest occurrence of such energy-saving aerial strategy. Anat Rec, 303:716-731, 2020. © 2019 American Association for Anatomy.

RevDate: 2021-03-09
CmpDate: 2020-02-25

Gao T, Yin X, Shih C, et al (2019)

New insects feeding on dinosaur feathers in mid-Cretaceous amber.

Nature communications, 10(1):5424.

Due to a lack of Mesozoic fossil records, the origins and early evolution of feather-feeding behaviors by insects are obscure. Here, we report ten nymph specimens of a new lineage of insect, Mesophthirus engeli gen et. sp. nov. within Mesophthiridae fam. nov. from the mid-Cretaceous (ca. 100 Mya) Myanmar (Burmese) amber. This new insect clade shows a series of ectoparasitic morphological characters such as tiny wingless body, head with strong chewing mouthparts, robust and short antennae having long setae, legs with only one single tarsal claw associated with two additional long setae, etc. Most significantly, these insects are preserved with partially damaged dinosaur feathers, the damage of which was probably made by these insects' integument-feeding behaviors. This finding demonstrates that feather-feeding behaviors of insects originated at least in mid-Cretaceous, accompanying the radiation of feathered dinosaurs including early birds.

RevDate: 2020-12-01
CmpDate: 2019-12-12

Wang X, Tang HK, JA Clarke (2019)

Flight, symmetry and barb angle evolution in the feathers of birds and other dinosaurs.

Biology letters, 15(12):20190622.

There has been much discussion over whether basal birds (e.g. Archaeopteryx and Confuciusornis) exhibited active flight. A recent study of barb angles has suggested they likely could not but instead may have exhibited a gliding phase. Pennaceous primary flight feathers were proposed to show significant shifts in barb angle values of relevance to the inference of flight in these extinct taxa. However, evolutionary trends in the evolution of these barb angle traits in extant volant taxa were not analysed in a phylogenetic frame. Neither the ancestral crown avian condition nor the condition in outgroup dinosaurs with symmetrical feathers were assessed. Here, we expand the fossil sample and reanalyse these data in a phylogenetic frame. We show that extant taxa, including strong flyers (e.g. some songbirds), show convergence on trailing barb angles and barb angle asymmetry observed in Mesozoic taxa that were proposed not to be active fliers. Trailing barb angles in these Mesozoic taxa are similar to symmetrical feathers in outgroup dinosaurs, indicating that selective regimes acted to modify primarily the leading-edge barb angles. These trends inform dynamics in feather shape evolution and challenge the notion that barb angle and barb angle ratios in extant birds directly inform the reconstruction of function in extinct stem taxa.

RevDate: 2021-01-10
CmpDate: 2020-05-20

Carroll NR, Chiappe LM, DJ Bottjer (2019)

Mid-Cretaceous amber inclusions reveal morphogenesis of extinct rachis-dominated feathers.

Scientific reports, 9(1):18108.

We describe three-dimensionally preserved feathers in mid-Cretaceous Burmese amber that share macro-morphological similarities (e.g., proportionally wide rachis with a "medial stripe") with lithic, two-dimensionally preserved rachis-dominated feathers, first recognized in the Jehol Biota. These feathers in amber reveal a unique ventrally concave and dorsoventrally thin rachis, and a dorsal groove (sometimes pigmented) that we identify as the "medial stripe" visible in many rachis-dominated rectrices of Mesozoic birds. The distally pennaceous portion of these feathers shows differentiated proximal and distal barbules, the latter with hooklets forming interlocking barbs. Micro-CT scans and transverse sections demonstrate the absence of histodifferentiated cortex and medullary pith of the rachis and barb rami. The highly differentiated barbules combined with the lack of obvious histodifferentiation of the barb rami or rachis suggests that these feathers could have been formed without the full suite and developmental interplay of intermediate filament alpha keratins and corneous beta-proteins that is employed in the cornification process of modern feathers. This study thus highlights how the development of these feathers might have differed from that of their modern counterparts, namely in the morphogenesis of the ventral components of the rachis and barb rami. We suggest that the concave ventral surface of the rachis of these Cretaceous feathers is not homologous with the ventral groove of modern rachises. Our study of these Burmese feathers also confirms previous claims, based on two-dimensional fossils, that they correspond to an extinct morphotype and it cautions about the common practice of extrapolating developmental aspects (and mechanical attributes) of modern feathers to those of stem birds (and their dinosaurian outgroups) because the latter need not to have developed through identical pathways.

RevDate: 2020-11-28
CmpDate: 2020-05-27

Chang WL, Wu H, Chiu YK, et al (2019)

The Making of a Flight Feather: Bio-architectural Principles and Adaptation.

Cell, 179(6):1409-1423.e17.

The evolution of flight in feathered dinosaurs and early birds over millions of years required flight feathers whose architecture features hierarchical branches. While barb-based feather forms were investigated, feather shafts and vanes are understudied. Here, we take a multi-disciplinary approach to study their molecular control and bio-architectural organizations. In rachidial ridges, epidermal progenitors generate cortex and medullary keratinocytes, guided by Bmp and transforming growth factor β (TGF-β) signaling that convert rachides into adaptable bilayer composite beams. In barb ridges, epidermal progenitors generate cylindrical, plate-, or hooklet-shaped barbule cells that form fluffy branches or pennaceous vanes, mediated by asymmetric cell junction and keratin expression. Transcriptome analyses and functional studies show anterior-posterior Wnt2b signaling within the dermal papilla controls barbule cell fates with spatiotemporal collinearity. Quantitative bio-physical analyses of feathers from birds with different flight characteristics and feathers in Burmese amber reveal how multi-dimensional functionality can be achieved and may inspire future composite material designs. VIDEO ABSTRACT.

RevDate: 2023-02-01

Roy A, Pittman M, Saitta ET, et al (2020)

Recent advances in amniote palaeocolour reconstruction and a framework for future research.

Biological reviews of the Cambridge Philosophical Society, 95(1):22-50.

Preserved melanin pigments have been discovered in fossilised integumentary appendages of several amniote lineages (fishes, frogs, snakes, marine reptiles, non-avialan dinosaurs, birds, and mammals) excavated from lagerstätten across the globe. Melanisation is a leading factor in organic integument preservation in these fossils. Melanin in extant vertebrates is typically stored in rod- to sphere-shaped, lysosome-derived, membrane-bound vesicles called melanosomes. Black, dark brown, and grey colours are produced by eumelanin, and reddish-brown colours are produced by phaeomelanin. Specific morphotypes and nanostructural arrangements of melanosomes and their relation to the keratin matrix in integumentary appendages create the so-called 'structural colours'. Reconstruction of colour patterns in ancient animals has opened an exciting new avenue for studying their life, behaviour and ecology. Modern relationships between the shape, arrangement, and size of avian melanosomes, melanin chemistry, and feather colour have been applied to reconstruct the hues and colour patterns of isolated feathers and plumages of the dinosaurs Anchiornis, Sinosauropteryx, and Microraptor in seminal papers that initiated the field of palaeocolour reconstruction. Since then, further research has identified countershading camouflage patterns, and informed subsequent predictions on the ecology and behaviour of these extinct animals. However, palaeocolour reconstruction remains a nascent field, and current approaches have considerable potential for further refinement, standardisation, and expansion. This includes detailed study of non-melanic pigments that might be preserved in fossilised integuments. A common issue among existing palaeocolour studies is the lack of contextualisation of different lines of evidence and the wide variety of techniques currently employed. To that end, this review focused on fossil amniotes: (i) produces an overarching framework that appropriately reconstructs palaeocolour by accounting for the chemical signatures of various pigments, morphology and local arrangement of pigment-bearing vesicles, pigment concentration, macroscopic colour patterns, and taphonomy; (ii) provides background context for the evolution of colour-producing mechanisms; and (iii) encourages future efforts in palaeocolour reconstructions particularly of less-studied groups such as non-dinosaur archosaurs and non-archosaur amniotes.

RevDate: 2021-02-08
CmpDate: 2021-02-08

Currie PJ, DC Evans (2020)

Cranial Anatomy of New Specimens of Saurornitholestes langstoni (Dinosauria, Theropoda, Dromaeosauridae) from the Dinosaur Park Formation (Campanian) of Alberta.

Anatomical record (Hoboken, N.J. : 2007), 303(4):691-715.

The holotype of the dromaeosaurid Saurornitholestes langstoni was described in 1978 on the basis of fewer than 30 associated cranial and postcranial bones of a single individual from Dinosaur Provincial Park. Four additional partial skeletons of Saurornitholestes were recovered from Campanian (Upper Cretaceous) beds of Alberta and Montana over the next 25 years, although reasonably complete skeletons remained elusive, and virtually nothing was known about the skull. The lack of truly diagnostic material has been problematic, and the relationships of Saurornitholestes to other dromaeosaurids have been difficult to resolve because of the incomplete knowledge of its anatomy. In 2014, an almost complete skeleton, including the skull, was collected less than a kilometer from where the holotype had been found. Although similar in body size to Velociraptor, the facial region of the skull is relatively shorter, taller, and wider. The nasals are pneumatic. The premaxillary teeth are distinctive, and teeth previously identified in the Dinosaur Park Formation as Zapsalis abradens can now be identified as the second premaxillary tooth of S. langstoni. Morphology and wear patterns suggest that these may have been specialized for preening feathers. Many traits define a Campanian North American clade, Saurornitholestinae, that is distinct from an Asian clade that includes Velociraptor (Velociraptorinae). This new information on the skull allows a more complete evaluation of its systematic position within the Dromaeosauridae and supports the suggestion of at least two major faunal interchanges between Asia and North America during the Cretaceous. Anat Rec, 303:691-715, 2020. © 2019 American Association for Anatomy.

RevDate: 2020-08-18
CmpDate: 2020-08-18

Persons WS, PJ Currie (2019)

Feather evolution exemplifies sexually selected bridges across the adaptive landscape.

Evolution; international journal of organic evolution, 73(9):1686-1694.

Over the last two decades, paleontologists have pieced together the early evolutionary history of feathers. Simple hair-like feathers served as insulating pelage, but the first feathers with complex branching structures and a plainer form evolved for the purpose of sexual display. The evolution of these complex display feathers was essential to the later evolution of flight. Feathers illustrate how sexual selection can generate complex novel phenotypes, which are then available for natural selection to modify and direct toward novel functions. In the longstanding metaphor of the adaptive landscape, sexual selection is a means by which lineages resting on one adaptive peak may gradually bridge a gap to another peak, without the landscape itself being first altered by environmental changes.

RevDate: 2020-07-10
CmpDate: 2020-07-10

O'Connor J, Zheng X, Dong L, et al (2019)

Microraptor with Ingested Lizard Suggests Non-specialized Digestive Function.

Current biology : CB, 29(14):2423-2429.e2.

Direct indicators of diet and predator-prey relationships are exceedingly rare in the fossil record [1, 2]. However, it is through such traces that we can best understand trophic interactions in ancient ecosystems [3], confirm dietary inferences derived from skeletal morphologies [4], and clarify behavioral and ecological interpretations [5]. Here, we identify a previously unrecognized lizard species in the abdomen of a specimen of Microraptor zhaoianus, a small, volant dromaeosaurid (Paraves) with asymmetrical flight feathers on both its forelimbs and hindlimbs from the Early Cretaceous Jehol Biota [6-8]. The lizard is largely complete and articulated, confirming the current perception of Microraptor as an agile opportunistic predator that, like extant reptiles, including raptorial birds, ingested small prey whole and head first [9]. The lizard can be readily distinguished from previously recognized Early Cretaceous species based on its unusual widely spaced and brachydont dentition. Phylogenetic analysis suggests Indrasaurus wangi gen. et sp. nov. is a basal scleroglossan closely related to the slightly older Liushusaurus [10]. Comparison of ingested remains preserved across Paraves suggests that dromaeosaurids retained the plesiomorphic condition in which ingested prey were fully digested, rather than egested, as has been demonstrated was the case in the probable troodontid Anchiornis [11]. This supports a closer relationship between Aves and Anchiornis [12, 13] and suggests that flight did not precipitate the evolution of pellet egestion in Paraves and that the evolution of the "modern avian" digestive system in paravians was highly homoplastic [14]. A preliminary Jehol food web is reconstructed from current data.

RevDate: 2020-07-10
CmpDate: 2020-07-10

Xing L, O'Connor JK, Chiappe LM, et al (2019)

A New Enantiornithine Bird with Unusual Pedal Proportions Found in Amber.

Current biology : CB, 29(14):2396-2401.e2.

Recent discoveries of vertebrate remains trapped in middle Cretaceous amber from northern Myanmar [1, 2] have provided insights into the morphology of soft-tissue structures in extinct animals [3-7], in particular, into the evolution and paleobiology of early birds [4, 8, 9]. So far, five bird specimens have been described from Burmese amber: two isolated wings, an isolated foot with wing fragment, and two partial skeletons [4, 8-10]. Most of these specimens contain the remains of juvenile enantiornithine birds [4]. Here, we describe a new specimen of enantiornithine bird in amber, collected at the Angbamo locality in the Hukawng Valley. The new specimen includes a partial right hindlimb and remiges from an adult or subadult bird. Its foot, of which the third digit is much longer than the second and fourth digits, is distinct from those of all other currently recognized Mesozoic and extant birds. Based on the autapomorphic foot morphology, we erect a new taxon, Elektorornis chenguangi gen. et sp. nov. We suggest that the elongated third digit was employed in a unique foraging strategy, highlighting the bizarre morphospace in which early birds operated.

RevDate: 2022-04-20
CmpDate: 2019-12-23

Shawkey MD, L D'Alba (2019)

Egg pigmentation probably has an early Archosaurian origin.

Nature, 570(7761):E43-E45.

RevDate: 2019-12-17
CmpDate: 2019-12-17

Benton MJ, Dhouailly D, Jiang B, et al (2019)

The Early Origin of Feathers.

Trends in ecology & evolution, 34(9):856-869.

Feathers have long been regarded as the innovation that drove the success of birds. However, feathers have been reported from close dinosaurian relatives of birds, and now from ornithischian dinosaurs and pterosaurs, the cousins of dinosaurs. Incomplete preservation makes these reports controversial. If true, these findings shift the origin of feathers back 80 million years before the origin of birds. Gene regulatory networks show the deep homology of scales, feathers, and hairs. Hair and feathers likely evolved in the Early Triassic ancestors of mammals and birds, at a time when synapsids and archosaurs show independent evidence of higher metabolic rates (erect gait and endothermy), as part of a major resetting of terrestrial ecosystems following the devastating end-Permian mass extinction.

RevDate: 2021-02-04
CmpDate: 2020-01-21

Wang M, O'Connor JK, Xu X, et al (2019)

A new Jurassic scansoriopterygid and the loss of membranous wings in theropod dinosaurs.

Nature, 569(7755):256-259.

Powered flight evolved independently in vertebrates in the pterosaurs, birds and bats, each of which has a different configuration of the bony elements and epidermal structures that form the wings[1,2]. Whereas the early fossil records of pterosaurs and bats are sparse, mounting evidence (primarily from China) of feathered non-avian dinosaurs and stemward avians that derive primarily from the Middle-Upper Jurassic and Lower Cretaceous periods has enabled the slow piecing together of the origins of avian flight[3,4]. These fossils demonstrate that, close to the origin of flight, dinosaurs closely related to birds were experimenting with a diversity of wing structures[3,5]. One of the most surprising of these is that of the scansoriopterygid (Theropoda, Maniraptora) Yi qi, which has membranous wings-a flight apparatus that was previously unknown among theropods but that is used by both the pterosaur and bat lineages[6]. This observation was not universally accepted[7]. Here we describe a newly identified scansoriopterygid-which we name Ambopteryx longibrachium, gen. et sp. nov.-from the Upper Jurassic period. This specimen provides support for the widespread existence of membranous wings and the styliform element in the Scansoriopterygidae, as well as evidence for the diet of this enigmatic theropod clade. Our analyses show that marked changes in wing architecture evolved near the split between the Scansoriopterygidae and the avian lineage, as the two clades travelled along very different paths to becoming volant. The membranous wings supported by elongate forelimbs that are present in scansoriopterygids probably represent a short-lived experimentation with volant behaviour, and feathered wings were ultimately favoured during the later evolution of Paraves.

RevDate: 2020-03-09
CmpDate: 2019-11-15

Talori YS, Zhao JS, Liu YF, et al (2019)

Identification of avian flapping motion from non-volant winged dinosaurs based on modal effective mass analysis.

PLoS computational biology, 15(5):e1006846.

The origin of avian flight is one of the most controversial debates in Paleontology. This paper investigates the wing performance of Caudipteryx, the most basal non-volant dinosaur with pennaceous feathered forelimbs by using modal effective mass theory. From a mechanical standpoint, the forced vibrations excited by hindlimb locomotion stimulate the movement of wings, creating a flapping-like motion in response. This shows that the origin of the avian flight stroke should lie in a completely natural process of active locomotion on the ground. In this regard, flapping in the history of evolution of avian flight should have already occurred when the dinosaurs were equipped with pennaceous remiges and rectrices. The forced vibrations provided the initial training for flapping the feathered wings of theropods similar to Caudipteryx.

RevDate: 2021-01-09
CmpDate: 2020-10-07

Qiu R, Wang X, Wang Q, et al (2019)

A new caudipterid from the Lower Cretaceous of China with information on the evolution of the manus of Oviraptorosauria.

Scientific reports, 9(1):6431.

Caudipteridae is a basal clade of Oviraptorosauria, all known species from the Early Cretaceous Jehol Biota of northeastern China. They were one of the first feathered dinosaur groups discovered, and possessed avian-like pennaceous remiges and rectrices. Their discovery provided significant information on early oviraptorosaurian evolution and the origins of birds and feathers. Here we describe a new caudipterid species Xingtianosaurus ganqi gen. et sp. nov. from the Lower Cretaceous Yixian Formation of Liaoning Province, China. This new taxon differs from other caudipterids by a small pleurocoel close to the dorsal edge of the lateral surface of the dorsal vertebrate centrum, a humerus longer than the scapula, a proportionally long ulna, a relatively small radiale angle, and a relatively short metacarpal I. The phylogenetic results shows X. ganqi is an early diverging caudipterid. It exhibits a mosaic morphology, providing new morphological information on early manual evolution of Oviraptorosauria, and giving new light on the evolution of radiale angle among Coelurosauria.

RevDate: 2021-01-09
CmpDate: 2020-10-13

McCoy VE, Gabbott SE, Penkman K, et al (2019)

Ancient amino acids from fossil feathers in amber.

Scientific reports, 9(1):6420.

Ancient protein analysis is a rapidly developing field of research. Proteins ranging in age from the Quaternary to Jurassic are being used to answer questions about phylogeny, evolution, and extinction. However, these analyses are sometimes contentious, and focus primarily on large vertebrates in sedimentary fossilisation environments; there are few studies of protein preservation in fossils in amber. Here we show exceptionally slow racemisation rates during thermal degradation experiments of resin enclosed feathers, relative to previous thermal degradation experiments of ostrich eggshell, coral skeleton, and limpet shell. We also recover amino acids from two specimens of fossil feathers in amber. The amino acid compositions are broadly similar to those of degraded feathers, but concentrations are very low, suggesting that much of the original protein has been degraded and lost. High levels of racemisation in more apolar, slowly racemising amino acids suggest that some of the amino acids were ancient and therefore original. Our findings indicate that the unique fossilisation environment inside amber shows potential for the recovery of ancient amino acids and proteins.

RevDate: 2020-03-09
CmpDate: 2019-09-05

Eliason CM, JA Clarke (2018)

Metabolic physiology explains macroevolutionary trends in the melanic colour system across amniotes.

Proceedings. Biological sciences, 285(1893):20182014.

Metabolism links organisms to their environment through its effects on thermoregulation, feeding behaviour and energetics. Genes involved in metabolic processes have known pleiotropic effects on some melanic colour traits. Understanding links between physiology and melanic colour is critical for understanding the role of, and potential constraints on, colour production. Despite considerable variation in metabolic rates and presumed ancestral melanic coloration in vertebrates, few studies have looked at a potential relationship between these two systems in a comparative framework. Here, we test the hypothesis that changes in melanosome shape in integumentary structures track metabolic rate variation across amniotes. Using multivariate comparative analyses and incorporating both extant and fossil taxa, we find significantly faster rates of melanosome shape evolution in taxa with high metabolic rates, as well as both colour- and clade-specific differences in the relationship between metabolic rate and melanosome shape. Phylogenetic tests recover an expansion in melanosome morphospace in maniraptoran dinosaurs, as well as rate shifts within birds (in songbirds) and mammals. These findings indicate another core phenotype influenced by metabolic changes in vertebrates. They also provide a framework for testing clade-specific gene expression patterns in the melanocortin system and may improve colour reconstructions in extinct taxa.

RevDate: 2021-01-09
CmpDate: 2020-10-05

Griffin DK, Larkin DM, RE O'Connor (2020)

Time lapse: A glimpse into prehistoric genomics.

European journal of medical genetics, 63(2):103640.

For the purpose of this review, 'time-lapse' refers to the reconstruction of ancestral (in this case dinosaur) karyotypes using genome assemblies of extant species. Such reconstructions are only usually possible when genomes are assembled to 'chromosome level' i.e. a complete representation of all the sequences, correctly ordered contiguously on each of the chromosomes. Recent paleontological evidence is very clear that birds are living dinosaurs, the latest example of dinosaurs emerging from a catastrophic extinction event. Non-avian dinosaurs (ever present in the public imagination through art, and broadcast media) emerged some 240 million years ago and have displayed incredible phenotypic diversity. Here we report on our recent studies to infer the overall karyotype of the Theropod dinosaur lineage from extant avian chromosome level genome assemblies. Our work first focused on determining the likely karyotype of the avian ancestor (most likely a chicken-sized, two-legged, feathered, land dinosaur from the Jurassic period) finding karyotypic similarity to the chicken. We then took the work further to determine the likely karyotype of the bird-lizard ancestor and the chromosomal changes (chiefly translocations and inversions) that occurred between then and modern birds. A combination of bioinformatics and cross-species fluorescence in situ hybridization (zoo-FISH) uncovered a considerable number of translocations and fissions from a 'lizard-like' genome structure of 2n = 36-46 to one similar to that of soft-shelled turtles (2n = 66) from 275 to 255 million years ago (mya). Remarkable karyotypic similarities between some soft-shelled turtles and chicken suggests that there were few translocations from the bird-turtle ancestor (plus ∼7 fissions) through the dawn of the dinosaurs and pterosaurs, through the theropod linage and on to most to modern birds. In other words, an avian-like karyotype was in place about 240mya when the dinosaurs and pterosaurs first emerged. We mapped 49 chromosome inversions from then to the present day, uncovering some gene ontology enrichment in evolutionary breakpoint regions. This avian-like karyotype with its many (micro)chromosomes provides the basis for variation (the driver of natural selection) through increased random segregation and recombination. It may therefore contribute to the ability of dinosaurs to survive multiple extinction events, emerging each time as speciose and diverse.

RevDate: 2020-08-25
CmpDate: 2020-08-25

Eastick DL, Tattersall GJ, Watson SJ, et al (2019)

Cassowary casques act as thermal windows.

Scientific reports, 9(1):1966.

Many ideas have been put forward for the adaptive value of the cassowary casque; and yet, its purpose remains speculative. Homeothermic animals elevate body temperature through metabolic heat production. Heat gain must be offset by heat loss to maintain internal temperatures within a range for optimal performance. Living in a tropical climate, cassowaries, being large bodied, dark feathered birds, are under thermal pressure to offload heat. We tested the original hypothesis that the casque acts as a thermal window. With infrared thermographic analyses of living cassowaries over an expansive range of ambient temperatures, we provide evidence that the casque acts as a thermal radiator, offloading heat at high temperatures and restricting heat loss at low temperatures. Interestingly, at intermediate temperatures, the casque appears thermally heterogeneous, with the posterior of the casque heating up before the front half. These findings might have implications for the function of similar structures in avian and non-avian dinosaurs.

RevDate: 2019-08-21
CmpDate: 2019-08-21

Campos APC, de Carvalho RT, Straker LC, et al (2019)

Combined microscopy and spectroscopy techniques to characterize a fossilized feather with minimal damage to the specimen.

Micron (Oxford, England : 1993), 120:17-24.

The study of fossil feathers has been revitalized in the last few decades and has contributed significantly to paleontological studies of dinosaurs and birds. Specific morphological and physicochemical characteristics of the microscale structures of feathers and the protein keratin are key targets when preserved during the fossilization process. Keratin is a fibrous protein that composes some hard tissues such as hair, nails and feathers. It is part of the so called intermediate filaments inside keratinocyte cells and is rich in sulfur containing amino acid cysteine. To date, different microscopy and analytical methods have been used for the analysis and detailed characterization and classification of feathers. However, in this work we showed that analytical optical and electron microscopies can be quick and precise methods with minimal effects on the sample during analysis. This association of different approaches on the same sample results in correlative data albeit in different length scales. Intracellular bodies called melanosomes originally present in melanocyte cells were identified with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), and had well-defined orientation and a mean aspect ratio comparable to melanosomes extant in dark feathers. The detection of sulphur in melanosomes via Energy Dispersive Spectroscopy both in SEM and TEM shows that, along the fossilization process, sulphur from the degraded keratin matrix could have been trapped inside the melanosomes. Chemical groups that make up keratin and melanin in the fossil sample were detected via FT-IR Spectroscopy and Confocal Laser Scanning Microscopy (CLSM). The use of combined analytical microscopy techniques can contribute significantly to the study of fossils generating precise results with minimum damage to the original sample.

RevDate: 2020-03-09
CmpDate: 2020-01-09

Havstad JC, NA Smith (2019)

Fossils with Feathers and Philosophy of Science.

Systematic biology, 68(5):840-851.

The last half century of paleornithological research has transformed the way that biologists perceive the evolutionary history of birds. This transformation has been driven, since 1969, by a series of exciting fossil discoveries combined with intense scientific debate over how best to interpret these discoveries. Ideally, as evidence accrues and results accumulate, interpretive scientific agreement forms. But this has not entirely happened in the debate over avian origins: the accumulation of scientific evidence and analyses has had some effect, but not a conclusive one, in terms of resolving the question of avian origins. Although the majority of biologists have come to accept that birds are dinosaurs, there is lingering and, in some quarters, strident opposition to this view. In order to both understand the ongoing disagreement about avian origins and generate a prediction about the future of the debate, here we use a revised model of scientific practice to assess the current and historical state of play surrounding the topic of bird evolutionary origins. Many scientists are familiar with the metascientific scholars Sir Karl Popper and Thomas Kuhn, and these are the primary figures that have been appealed to so far, in prior attempts to assess the dispute. But we demonstrate that a variation of Imre Lakatos's model of progressive versus degenerative research programmes provides a novel and productive assessment of the debate. We establish that a refurbished Lakatosian account both explains the intractability of the dispute and predicts a likely outcome for the debate about avian origins. In short, here, we offer a metascientific tool for rationally assessing competing theories-one that allows researchers involved in seemingly intractable scientific disputes to advance their debates.

RevDate: 2020-10-01

Cincotta A, Pestchevitskaya EB, Sinitsa SM, et al (2019)

The rise of feathered dinosaurs: Kulindadromeus zabaikalicus, the oldest dinosaur with 'feather-like' structures.

PeerJ, 7:e6239.

Diverse epidermal appendages including grouped filaments closely resembling primitive feathers in non-avian theropods, are associated with skeletal elements in the primitive ornithischian dinosaur Kulindadromeus zabaikalicus from the Kulinda locality in south-eastern Siberia. This discovery suggests that "feather-like" structures did not evolve exclusively in theropod dinosaurs, but were instead potentially widespread in the whole dinosaur clade. The dating of the Kulinda locality is therefore particularly important for reconstructing the evolution of "feather-like" structures in dinosaurs within a chronostratigraphic framework. Here we present the first dating of the Kulinda locality, combining U-Pb analyses (LA-ICP-MS) on detrital zircons and monazites from sedimentary rocks of volcaniclastic origin and palynological observations. Concordia ages constrain the maximum age of the volcaniclastic deposits at 172.8 ± 1.6 Ma, corresponding to the Aalenian (Middle Jurassic). The palynological assemblage includes taxa that are correlated to Bathonian palynozones from western Siberia, and therefore constrains the minimum age of the deposits. The new U-Pb ages, together with the palynological data, provide evidence of a Bathonian age-between 168.3 ± 1.3 Ma and 166.1 ± 1.2 Ma-for Kulindadromeus. This is older than the previous Late Jurassic to Early Cretaceous ages tentatively based on local stratigraphic correlations. A Bathonian age is highly consistent with the phylogenetic position of Kulindadromeus at the base of the neornithischian clade and suggests that cerapodan dinosaurs originated in Asia during the Middle Jurassic, from a common ancestor that closely looked like Kulindadromeus. Our results consequently show that Kulindadromeus is the oldest known dinosaur with "feather-like" structures discovered so far.

RevDate: 2020-08-13
CmpDate: 2020-08-13

Kaye TG, Pittman M, Mayr G, et al (2019)

Detection of lost calamus challenges identity of isolated Archaeopteryx feather.

Scientific reports, 9(1):1182.

In 1862, a fossil feather from the Solnhofen quarries was described as the holotype of the iconic Archaeopteryx lithographica. The isolated feather's identification has been problematic, and the fossil was considered either a primary, secondary or, most recently, a primary covert. The specimen is surrounded by the 'mystery of the missing quill'. The calamus described in the original paper is unseen today, even under x-ray fluorescence and UV imaging, challenging its original existence. We answer this question using Laser-Stimulated Fluorescence (LSF) through the recovery of the geochemical halo from the original calamus matching the published description. Our study therefore shows that new techniques applied to well-studied iconic fossils can still provide valuable insights. The morphology of the complete feather excludes it as a primary, secondary or tail feather of Archaeopteryx. However, it could be a covert or a contour feather, especially since the latter are not well known in Archaeopteryx. The possibility remains that it stems from a different feathered dinosaur that lived in the Solnhofen Archipelago. The most recent analysis of the isolated feather considers it to be a primary covert. If this is the case, it lacks a distinct s-shaped centerline found in modern primary coverts that appears to be documented here for the first time.

RevDate: 2020-07-24
CmpDate: 2020-07-24

Xing L, McKellar RC, O'Connor JK, et al (2019)

A fully feathered enantiornithine foot and wing fragment preserved in mid-Cretaceous Burmese amber.

Scientific reports, 9(1):927.

Over the last three years, Burmese amber (~99 Ma, from Myanmar) has provided a series of immature enantiornithine skeletal remains preserved in varying developmental stages and degrees of completeness. These specimens have improved our knowledge based on compression fossils in Cretaceous sedimentary rocks, adding details of three-dimensional structure and soft tissues that are rarely preserved elsewhere. Here we describe a remarkably well-preserved foot, accompanied by part of the wing plumage. These body parts were likely dismembered, entering the resin due to predatory or scavenging behaviour by a larger animal. The new specimen preserves contour feathers on the pedal phalanges together with enigmatic scutellae scale filament (SSF) feathers on the foot, providing direct analogies to the plumage patterns observed in modern birds, and those cultivated through developmental manipulation studies. Ultimately, this connection may allow researchers to observe how filamentous dinosaur 'protofeathers' developed-testing theories using evolutionary holdovers in modern birds.

RevDate: 2020-03-09
CmpDate: 2019-05-03

Pan Y, Zheng W, Sawyer RH, et al (2019)

The molecular evolution of feathers with direct evidence from fossils.

Proceedings of the National Academy of Sciences of the United States of America, 116(8):3018-3023.

Dinosaur fossils possessing integumentary appendages of various morphologies, interpreted as feathers, have greatly enhanced our understanding of the evolutionary link between birds and dinosaurs, as well as the origins of feathers and avian flight. In extant birds, the unique expression and amino acid composition of proteins in mature feathers have been shown to determine their biomechanical properties, such as hardness, resilience, and plasticity. Here, we provide molecular and ultrastructural evidence that the pennaceous feathers of the Jurassic nonavian dinosaur Anchiornis were composed of both feather β-keratins and α-keratins. This is significant, because mature feathers in extant birds are dominated by β-keratins, particularly in the barbs and barbules forming the vane. We confirm here that feathers were modified at both molecular and morphological levels to obtain the biomechanical properties for flight during the dinosaur-bird transition, and we show that the patterns and timing of adaptive change at the molecular level can be directly addressed in exceptionally preserved fossils in deep time.

RevDate: 2022-04-16
CmpDate: 2019-04-15

D'Alba L (2019)

Pterosaur plumage.

Nature ecology & evolution, 3(1):12-13.

RevDate: 2022-04-16
CmpDate: 2019-05-23

Yang Z, Jiang B, McNamara ME, et al (2019)

Pterosaur integumentary structures with complex feather-like branching.

Nature ecology & evolution, 3(1):24-30.

Pterosaurs were the first vertebrates to achieve true flapping flight, but in the absence of living representatives, many questions concerning their biology and lifestyle remain unresolved. Pycnofibres-the integumentary coverings of pterosaurs-are particularly enigmatic: although many reconstructions depict fur-like coverings composed of pycnofibres, their affinities and function are not fully understood. Here, we report the preservation in two anurognathid pterosaur specimens of morphologically diverse pycnofibres that show diagnostic features of feathers, including non-vaned grouped filaments and bilaterally branched filaments, hitherto considered unique to maniraptoran dinosaurs, and preserved melanosomes with diverse geometries. These findings could imply that feathers had deep evolutionary origins in ancestral archosaurs, or that these structures arose independently in pterosaurs. The presence of feather-like structures suggests that anurognathids, and potentially other pterosaurs, possessed a dense filamentous covering that probably functioned in thermoregulation, tactile sensing, signalling and aerodynamics.

RevDate: 2020-03-09
CmpDate: 2019-10-22

Talori YS, Liu YF, Zhao JS, et al (2018)

Winged forelimbs of the small theropod dinosaur Caudipteryx could have generated small aerodynamic forces during rapid terrestrial locomotion.

Scientific reports, 8(1):17854.

Pennaceous feathers capable of forming aerodynamic surfaces are characteristic of Pennaraptora, the group comprising birds and their closest relatives among non-avian dinosaurs. However, members of the basal pennaraptoran lineage Oviraptorosauria were clearly flightless, and the function of pennaceous feathers on the forelimb in oviraptorosaurs is still uncertain. In the basal oviraptorosaur Caudipteryx both the skeleton and the plumage, which includes pennaceous feathers forming wing-like arrangements on the forelimbs, are well known. We used mathematical analyses, computer simulations and experiments on a robot Caudipteryx with realistic wing proportions to test whether the wings of Caudipteryx could have generated aerodynamic forces useful in rapid terrestrial locomotion. These various approaches show that, if both wings were held in a fixed and laterally extended position, they would have produced only small amounts of lift and drag. A partial simulation of flapping while running showed similarly limited aerodynamic force production. These results are consistent with the possibility that pennaceous feathers first evolved for a non-locomotor function such as display, but the effects of flapping and the possible contribution of the wings during manoeuvres such as braking and turning remain to be more fully investigated.

RevDate: 2020-09-30

Saitta ET, Clapham C, J Vinther (2018)

Experimental subaqueous burial of a bird carcass and compaction of plumage.

Palaontologische zeitschrift, 92(4):727-732.

'Exceptional fossils' of dinosaurs preserving feathers have radically changed the way we view their paleobiology and the evolution of birds. Understanding how such soft tissues preserve is imperative to accurately interpreting the morphology of fossil feathers. Experimental taphonomy has been integral to such investigations. One such experiment used a printing press to mimic compaction, done subaerially and without sediment burial, and concluded that the leaking of bodily fluid could lead to the clumping of feathers by causing barbs to stick together such that they superficially resemble simpler, less derived, filamentous structures. Here we use a novel, custom-built experimental setup to more accurately mimic subaqueous burial and compaction under low-energy, fine-grain depositional environments applicable to the taphonomic settings most plumage-preserving 'exceptional fossils' are found in. We find that when submerged and subsequently buried and compacted, feathers do not clump together and they maintain their original arrangement. Submersion in fluid in and of itself does not lead to clumping of barbs; this would only occur upon pulling feathers out from water into air. Furthermore, sediment encases the feathers, fixing them in place during compaction. Thus, feather clumping that leads to erroneously plesiomorphic morphological interpretations may not be a taphonomic factor of concern when examining fossil feathers. Our current methodology is amenable to further improvements that will continue to more accurately mimic subaqueous burial and compaction, allowing for various hypothesis testing.

RevDate: 2019-06-06
CmpDate: 2019-06-06

Lindgren J, Sjövall P, Thiel V, et al (2018)

Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur.

Nature, 564(7736):359-365.

Ichthyosaurs are extinct marine reptiles that display a notable external similarity to modern toothed whales. Here we show that this resemblance is more than skin deep. We apply a multidisciplinary experimental approach to characterize the cellular and molecular composition of integumental tissues in an exceptionally preserved specimen of the Early Jurassic ichthyosaur Stenopterygius. Our analyses recovered still-flexible remnants of the original scaleless skin, which comprises morphologically distinct epidermal and dermal layers. These are underlain by insulating blubber that would have augmented streamlining, buoyancy and homeothermy. Additionally, we identify endogenous proteinaceous and lipid constituents, together with keratinocytes and branched melanophores that contain eumelanin pigment. Distributional variation of melanophores across the body suggests countershading, possibly enhanced by physiological adjustments of colour to enable photoprotection, concealment and/or thermoregulation. Convergence of ichthyosaurs with extant marine amniotes thus extends to the ultrastructural and molecular levels, reflecting the omnipresent constraints of their shared adaptation to pelagic life.

RevDate: 2019-05-20
CmpDate: 2019-05-20

Wiemann J, Yang TR, MA Norell (2018)

Dinosaur egg colour had a single evolutionary origin.

Nature, 563(7732):555-558.

Birds are the only living amniotes with coloured eggs[1-4], which have long been considered to be an avian innovation[1,3]. A recent study has demonstrated the presence of both red-brown protoporphyrin IX and blue-green biliverdin[5]-the pigments responsible for all the variation in avian egg colour-in fossilized eggshell of a nonavian dinosaur[6]. This raises the fundamental question of whether modern birds inherited egg colour from their nonavian dinosaur ancestors, or whether egg colour evolved independently multiple times. Here we present a phylogenetic assessment of egg colour in nonavian dinosaurs. We applied high-resolution Raman microspectroscopy to eggshells that represent all of the major clades of dinosaurs, and found that egg colour pigments were preserved in all eumaniraptorans: egg colour had a single evolutionary origin in nonavian theropod dinosaurs. The absence of colour in ornithischian and sauropod eggs represents a true signal rather than a taphonomic artefact. Pigment surface maps revealed that nonavian eumaniraptoran eggs were spotted and speckled, and colour pattern diversity in these eggs approaches that in extant birds, which indicates that reproductive behaviours in nonavian dinosaurs were far more complex than previously known[3]. Depth profiles demonstrated identical mechanisms of pigment deposition in nonavian and avian dinosaur eggs. Birds were not the first amniotes to produce coloured eggs: as with many other characteristics[7,8] this is an attribute that evolved deep within the dinosaur tree and long before the spectacular radiation of modern birds.

RevDate: 2020-09-29

Heers AM, Rankin JW, JR Hutchinson (2018)

Building a Bird: Musculoskeletal Modeling and Simulation of Wing-Assisted Incline Running During Avian Ontogeny.

Frontiers in bioengineering and biotechnology, 6:140.

Flapping flight is the most power-demanding mode of locomotion, associated with a suite of anatomical specializations in extant adult birds. In contrast, many developing birds use their forelimbs to negotiate environments long before acquiring "flight adaptations," recruiting their developing wings to continuously enhance leg performance and, in some cases, fly. How does anatomical development influence these locomotor behaviors? Isolating morphological contributions to wing performance is extremely challenging using purely empirical approaches. However, musculoskeletal modeling and simulation techniques can incorporate empirical data to explicitly examine the functional consequences of changing morphology by manipulating anatomical parameters individually and estimating their effects on locomotion. To assess how ontogenetic changes in anatomy affect locomotor capacity, we combined existing empirical data on muscle morphology, skeletal kinematics, and aerodynamic force production with advanced biomechanical modeling and simulation techniques to analyze the ontogeny of pectoral limb function in a precocial ground bird (Alectoris chukar). Simulations of wing-assisted incline running (WAIR) using these newly developed musculoskeletal models collectively suggest that immature birds have excess muscle capacity and are limited more by feather morphology, possibly because feathers grow more quickly and have a different style of growth than bones and muscles. These results provide critical information about the ontogeny and evolution of avian locomotion by (i) establishing how muscular and aerodynamic forces interface with the skeletal system to generate movement in morphing juvenile birds, and (ii) providing a benchmark to inform biomechanical modeling and simulation of other locomotor behaviors, both across extant species and among extinct theropod dinosaurs.

RevDate: 2020-10-01

Yang TR, Chen YH, Wiemann J, et al (2018)

Fossil eggshell cuticle elucidates dinosaur nesting ecology.

PeerJ, 6:e5144.

The cuticle layer consisting mainly of lipids and hydroxyapatite (HAp) atop the mineralized avian eggshell is a protective structure that prevents the egg from dehydration and microbial invasions. Previous ornithological studies have revealed that the cuticle layer is also involved in modulating the reflectance of eggshells in addition to pigments (protoporphyrin and biliverdin). Thus, the cuticle layer represents a crucial trait that delivers ecological signals. While present in most modern birds, direct evidence for cuticle preservation in stem birds and non-avian dinosaurs is yet missing. Here we present the first direct and chemical evidence for the preservation of the cuticle layer on dinosaur eggshells. We analyze several theropod eggshells from various localities, including oviraptorid Macroolithus yaotunensis eggshells from the Late Cretaceous deposits of Henan, Jiangxi, and Guangdong in China and alvarezsaurid Triprismatoolithus eggshell from the Two Medicine Formation of Montana, United States, with the scanning electron microscope (SEM), electron probe micro-analysis (EPMA), and Raman spectroscopy (RS). The elemental analysis with EPMA shows high concentration of phosphorus at the boundary between the eggshell and sediment, representing the hydroxyapatitic cuticle layer (HAp). Depletion of phosphorus in sediment excludes the allochthonous origin of the phosphorus in these eggshells. The chemometric analysis of Raman spectra collected from fossil and extant eggs provides further supportive evidence for the cuticle preservation in oviraptorid and probable alvarezsaurid eggshells. In accordance with our previous discovery of pigments preserved in Cretaceous oviraptorid dinosaur eggshells, we validate the cuticle preservation on dinosaur eggshells through deep time and offer a yet unexplored resource for chemical studies targeting the evolution of dinosaur nesting ecology. Our study also suggests that the cuticle structure can be traced far back to maniraptoran dinosaurs and enhance their reproductive success in a warm and mesic habitat such as Montana and southern China during the Late Cretaceous.

RevDate: 2019-10-22
CmpDate: 2019-10-21

Rashid DJ, Surya K, Chiappe LM, et al (2018)

Avian tail ontogeny, pygostyle formation, and interpretation of juvenile Mesozoic specimens.

Scientific reports, 8(1):9014.

The avian tail played a critical role in the evolutionary transition from long- to short-tailed birds, yet its ontogeny in extant birds has largely been ignored. This deficit has hampered efforts to effectively identify intermediate species during the Mesozoic transition to short tails. Here we show that fusion of distal vertebrae into the pygostyle structure does not occur in extant birds until near skeletal maturity, and mineralization of vertebral processes also occurs long after hatching. Evidence for post-hatching pygostyle formation is also demonstrated in two Cretaceous specimens, a juvenile enantiornithine and a subadult basal ornithuromorph. These findings call for reinterpretations of Zhongornis haoae, a Cretaceous bird hypothesized to be an intermediate in the long- to short-tailed bird transition, and of the recently discovered coelurosaur tail embedded in amber. Zhongornis, as a juvenile, may not yet have formed a pygostyle, and the amber-embedded tail specimen is reinterpreted as possibly avian. Analyses of relative pygostyle lengths in extant and Cretaceous birds suggests the number of vertebrae incorporated into the pygostyle has varied considerably, further complicating the interpretation of potential transitional species. In addition, this analysis of avian tail development reveals the generation and loss of intervertebral discs in the pygostyle, vertebral bodies derived from different kinds of cartilage, and alternative modes of caudal vertebral process morphogenesis in birds. These findings demonstrate that avian tail ontogeny is a crucial parameter specifically for the interpretation of Mesozoic specimens, and generally for insights into vertebrae formation.

RevDate: 2019-05-25
CmpDate: 2018-12-11

McNamara ME, Zhang F, Kearns SL, et al (2018)

Fossilized skin reveals coevolution with feathers and metabolism in feathered dinosaurs and early birds.

Nature communications, 9(1):2072.

Feathers are remarkable evolutionary innovations that are associated with complex adaptations of the skin in modern birds. Fossilised feathers in non-avian dinosaurs and basal birds provide insights into feather evolution, but how associated integumentary adaptations evolved is unclear. Here we report the discovery of fossil skin, preserved with remarkable nanoscale fidelity, in three non-avian maniraptoran dinosaurs and a basal bird from the Cretaceous Jehol biota (China). The skin comprises patches of desquamating epidermal corneocytes that preserve a cytoskeletal array of helically coiled α-keratin tonofibrils. This structure confirms that basal birds and non-avian dinosaurs shed small epidermal flakes as in modern mammals and birds, but structural differences imply that these Cretaceous taxa had lower body heat production than modern birds. Feathered epidermis acquired many, but not all, anatomically modern attributes close to the base of the Maniraptora by the Middle Jurassic.

RevDate: 2019-03-13
CmpDate: 2018-04-03

Voeten DFAE, Cubo J, de Margerie E, et al (2018)

Wing bone geometry reveals active flight in Archaeopteryx.

Nature communications, 9(1):923.

Archaeopteryx is an iconic fossil taxon with feathered wings from the Late Jurassic of Germany that occupies a crucial position for understanding the early evolution of avian flight. After over 150 years of study, its mosaic anatomy unifying characters of both non-flying dinosaurs and flying birds has remained challenging to interpret in a locomotory context. Here, we compare new data from three Archaeopteryx specimens obtained through phase-contrast synchrotron microtomography to a representative sample of archosaurs employing a diverse array of locomotory strategies. Our analyses reveal that the architecture of Archaeopteryx's wing bones consistently exhibits a combination of cross-sectional geometric properties uniquely shared with volant birds, particularly those occasionally utilising short-distance flapping. We therefore interpret that Archaeopteryx actively employed wing flapping to take to the air through a more anterodorsally posteroventrally oriented flight stroke than used by modern birds. This unexpected outcome implies that avian powered flight must have originated before the latest Jurassic.

RevDate: 2023-01-20

Xing L, O'Connor JK, McKellar RC, et al (2018)

A flattened enantiornithine in mid-Cretaceous Burmese amber: morphology and preservation.

Science bulletin, 63(4):235-243.

Cretaceous amber from Myanmar (∼99 Ma Burmese amber) has become a valuable supplement to the traditional skeletal record of small theropod dinosaurs preserved in sedimentary rocks, particularly for coelurosaurs and enantiornithines. The specimens recovered from this deposit preserve skeletal material and soft tissues in unmatched detail. This provides opportunities to study three-dimensional preservation of soft tissues, microstructure, and pigmentation patterns that are seldom available elsewhere in the fossil record. Ultimately, this line of research provides insights into life stages that are difficult to preserve, the ecology and appearance of the groups involved, and the evolutionary-development of structures such as feathers. Here we describe the most recent discovery from Burmese amber, an articulated skeleton of an enantiornithine bird. This individual has been sectioned along the coronal plane, providing a unique view inside multiple body regions. Osteological observations and plumage patterns support placement within the Enantiornithes, and suggest that the animal may have been a juvenile at the time of death. The specimen has a complex taphonomic history that includes exposure at the surface of a resin flow prior to encapsulation, and may include scavenging by some of the insects trapped within the same amber piece. The chemical composition observed along surface exposures and shallowly buried regions of the body indicate that the specimen has not undergone significant exchange with its surroundings. High iron concentrations are present in regions that preserve soft tissues as carbon films, and calcium distribution corresponds to regions where bones breach the surface of the amber.

RevDate: 2019-11-20

Peñalver E, Arillo A, Delclòs X, et al (2018)

Publisher Correction: Ticks parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages.

Nature communications, 9(1):472 pii:10.1038/s41467-018-02913-w.

The originally published version of this Article was updated shortly after publication to add the word 'Ticks' to the title, following its inadvertent removal during the production process. This has now been corrected in both the PDF and HTML versions of the Article.

RevDate: 2022-03-11

Kondo M, Sekine T, Miyakoshi T, et al (2018)

Flight feather development: its early specialization during embryogenesis.

Zoological letters, 4:2.

BACKGROUND: Flight feathers, a type of feather that is unique to extant/extinct birds and some non-avian dinosaurs, are the most evolutionally advanced type of feather. In general, feather types are formed in the second or later generation of feathers at the first and following molting, and the first molting begins at around two weeks post hatching in chicken. However, it has been stated in some previous reports that the first molting from the natal down feathers to the flight feathers is much earlier than that for other feather types, suggesting that flight feather formation starts as an embryonic event. The aim of this study was to determine the inception of flight feather morphogenesis and to identify embryological processes specific to flight feathers in contrast to those of down feathers.

RESULTS: We found that the second generation of feather that shows a flight feather-type arrangement has already started developing by chick embryonic day 18, deep in the skin of the flight feather-forming region. This was confirmed by shh gene expression that shows barb pattern, and the expression pattern revealed that the second generation of feather development in the flight feather-forming region seems to start by embryonic day 14. The first stage at which we detected a specific morphology of the feather bud in the flight feather-forming region was embryonic day 11, when internal invagination of the feather bud starts, while the external morphology of the feather bud is radial down-type.

CONCLUSION: The morphogenesis for the flight feather, the most advanced type of feather, has been drastically modified from the beginning of feather morphogenesis, suggesting that early modification of the embryonic morphogenetic process may have played a crucial role in the morphological evolution of this key innovation. Co-optation of molecular cues for axial morphogenesis in limb skeletal development may be able to modify morphogenesis of the feather bud, giving rise to flight feather-specific morphogenesis of traits.

RevDate: 2018-11-13
CmpDate: 2018-08-06

Negro JJ, Finlayson C, I Galván (2018)

Melanins in Fossil Animals: Is It Possible to Infer Life History Traits from the Coloration of Extinct Species?.

International journal of molecular sciences, 19(2):.

Paleo-colour scientists have recently made the transition from describing melanin-based colouration in fossil specimens to inferring life-history traits of the species involved. Two such cases correspond to counter-shaded dinosaurs: dark-coloured due to melanins dorsally, and light-coloured ventrally. We believe that colour reconstruction of fossils based on the shape of preserved microstructures-the majority of paleo-colour studies involve melanin granules-is not without risks. In addition, animals with contrasting dorso-ventral colouration may be under different selection pressures beyond the need for camouflage, including, for instance, visual communication or ultraviolet (UV) protection. Melanin production is costly, and animals may invest less in areas of the integument where pigments are less needed. In addition, melanocytes exposed to UV radiation produce more melanin than unexposed melanocytes. Pigment economization may thus explain the colour pattern of some counter-shaded animals, including extinct species. Even in well-studied extant species, their diversity of hues and patterns is far from being understood; inferring colours and their functions in species only known from one or few specimens from the fossil record should be exerted with special prudence.

RevDate: 2018-11-13
CmpDate: 2018-03-05

Hu D, Clarke JA, Eliason CM, et al (2018)

A bony-crested Jurassic dinosaur with evidence of iridescent plumage highlights complexity in early paravian evolution.

Nature communications, 9(1):217.

The Jurassic Yanliao theropods have offered rare glimpses of the early paravian evolution and particularly of bird origins, but, with the exception of the bizarre scansoriopterygids, they have shown similar skeletal and integumentary morphologies. Here we report a distinctive new Yanliao theropod species bearing prominent lacrimal crests, bony ornaments previously known from more basal theropods. It shows longer arm and leg feathers than Anchiornis and tail feathers with asymmetrical vanes forming a tail surface area even larger than that in Archaeopteryx. Nanostructures, interpreted as melanosomes, are morphologically similar to organized, platelet-shaped organelles that produce bright iridescent colours in extant birds. The new species indicates the presence of bony ornaments, feather colour and flight-related features consistent with proposed rapid character evolution and significant diversity in signalling and locomotor strategies near bird origins.

RevDate: 2019-01-10
CmpDate: 2018-11-16

Prondvai E, Godefroit P, Adriaens D, et al (2018)

Intraskeletal histovariability, allometric growth patterns, and their functional implications in bird-like dinosaurs.

Scientific reports, 8(1):258.

With their elongated forelimbs and variable aerial skills, paravian dinosaurs, a clade also comprising modern birds, are in the hotspot of vertebrate evolutionary research. Inferences on the early evolution of flight largely rely on bone and feather morphology, while osteohistological traits are usually studied to explore life-history characteristics. By sampling and comparing multiple homologous fore- and hind limb elements, we integrate for the first time qualitative and quantitative osteohistological approaches to get insight into the intraskeletal growth dynamics and their functional implications in five paravian dinosaur taxa, Anchiornis, Aurornis, Eosinopteryx, Serikornis, and Jeholornis. Our qualitative assessment implies a considerable diversity in allometric/isometric growth patterns among these paravians. Quantitative analyses show that neither taxa nor homologous elements have characteristic histology, and that ontogenetic stage, element size and the newly introduced relative element precocity only partially explain the diaphyseal histovariability. Still, Jeholornis, the only avialan studied here, is histologically distinct from all other specimens in the multivariate visualizations raising the hypothesis that its bone tissue characteristics may be related to its superior aerial capabilities compared to the non-avialan paravians. Our results warrant further research on the osteohistological correlates of flight and developmental strategies in birds and bird-like dinosaurs.

RevDate: 2020-10-01

Wilson PF, Smith MP, Hay J, et al (2018)

X-ray computed tomography (XCT) and chemical analysis (EDX and XRF) used in conjunction for cultural conservation: the case of the earliest scientifically described dinosaur Megalosaurus bucklandii.

Heritage science, 6(1):58.

This paper demonstrates the combined use of X-ray computed tomography (XCT), energy dispersive X-ray spectroscopy (EDX) and X-ray fluorescence (XRF) to evaluate the conservational history of the dentary (lower jaw) of Megalosaurus bucklandii Mantell, 1827, the first scientifically described dinosaur. Previous analysis using XCT revealed that the specimen had undergone at least two phases of repair using two different kinds of plaster, although their composition remained undetermined. Additional chemical analysis using EDX and XRF has allowed the determination of the composition of these unidentified plasters, revealing that they are of similar composition, composed dominantly of 'plaster of Paris' mixed with quartz sand and calcite, potentially from the matrix material of the Stonesfield Slate, with the trace presence of chlorine. One of the plasters unusually contains the pigment minium (naturally occurring lead tetroxide; Pb2 [2+]Pb[4+]O4) whilst the other seems to have an additional coating of barium hydroxide (Ba(OH)2), indicating that these likely represent two separate stages of repair. The potential of this combined approach for evaluating problematic museum objects for conservation is further discussed as is its usage in cultural heritage today.

RevDate: 2018-12-12
CmpDate: 2018-09-18

Peñalver E, Arillo A, Delclòs X, et al (2017)

parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages.

Nature communications, 8(1):1924.

Ticks are currently among the most prevalent blood-feeding ectoparasites, but their feeding habits and hosts in deep time have long remained speculative. Here, we report direct and indirect evidence in 99 million-year-old Cretaceous amber showing that hard ticks and ticks of the extinct new family Deinocrotonidae fed on blood from feathered dinosaurs, non-avialan or avialan excluding crown-group birds. A †Cornupalpatum burmanicum hard tick is entangled in a pennaceous feather. Two deinocrotonids described as †Deinocroton draculi gen. et sp. nov. have specialised setae from dermestid beetle larvae (hastisetae) attached to their bodies, likely indicating cohabitation in a feathered dinosaur nest. A third conspecific specimen is blood-engorged, its anatomical features suggesting that deinocrotonids fed rapidly to engorgement and had multiple gonotrophic cycles. These findings provide insight into early tick evolution and ecology, and shed light on poorly known arthropod-vertebrate interactions and potential disease transmission during the Mesozoic.

RevDate: 2019-02-15
CmpDate: 2019-02-15

Wu P, Yan J, Lai YC, et al (2018)

Multiple Regulatory Modules Are Required for Scale-to-Feather Conversion.

Molecular biology and evolution, 35(2):417-430.

The origin of feathers is an important question in Evo-Devo studies, with the eventual evolution of vaned feathers which are aerodynamic, allowing feathered dinosaurs and early birds to fly and venture into new ecological niches. Studying how feathers and scales are developmentally specified provides insight into how a new organ may evolve. We identified feather-associated genes using genomic analyses. The candidate genes were tested by expressing them in chicken and alligator scale forming regions. Ectopic expression of these genes induced intermediate morphotypes between scales and feathers which revealed several major morphogenetic events along this path: Localized growth zone formation, follicle invagination, epithelial branching, feather keratin differentiation, and dermal papilla formation. In addition to molecules known to induce feathers on scales (retinoic acid, β-catenin), we identified novel scale-feather converters (Sox2, Zic1, Grem1, Spry2, Sox18) which induce one or more regulatory modules guiding these morphogenetic events. Some morphotypes resemble filamentous appendages found in feathered dinosaur fossils, whereas others exhibit characteristics of modern avian feathers. We propose these morpho-regulatory modules were used to diversify archosaur scales and to initiate feather evolution. The regulatory combination and hierarchical integration may have led to the formation of extant feather forms. Our study highlights the importance of integrating discoveries between developmental biology and paleontology.

RevDate: 2018-08-08
CmpDate: 2018-08-08

Smithwick FM, Nicholls R, Cuthill IC, et al (2017)

Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal Heterogeneous Habitats in the Early Cretaceous Jehol Biota.

Current biology : CB, 27(21):3337-3343.e2.

Countershading is common across a variety of lineages and ecological time [1-4]. A dark dorsum and lighter ventrum helps to mask the three-dimensional shape of the body by reducing self-shadowing and decreasing conspicuousness, thus helping to avoid detection by predators and prey [1, 2, 4, 5]. The optimal countershading pattern is dictated by the lighting environment, which is in turn dependent upon habitat [1, 3, 5, 6]. With the discovery of fossil melanin [7, 8], it is possible to infer original color patterns from fossils, including countershading [3, 9, 10]. Applying these principles, we describe the pattern of countershading in the diminutive theropod dinosaur Sinosauropteryx from the Early Cretaceous Jehol Biota of Liaoning, China. From reconstructions based on exceptional fossils, the color pattern is compared to predicted optimal countershading transitions based on 3D reconstructions of the animal's abdomen, imaged in different lighting environments. Reconstructed patterns match well with those predicted for animals living in open habitats. Jehol is presumed to have been a predominantly closed forested environment [3, 11, 12], but our results indicate a more heterogeneous range of habitats. Sinosauropteryx is also shown to exhibit a "bandit mask," a common pattern in many living vertebrates, particularly birds, that serves multiple functions including camouflage [13-18]. Sinosauropteryx therefore shows multiple color pattern features likely related to the habitat in which it lived. Our results show how reconstructing the color of extinct animals can inform on their ecologies beyond what may be obvious from skeletal remains alone. VIDEO ABSTRACT.

RevDate: 2018-12-02
CmpDate: 2018-02-14

Pickrell J (2017)

Camouflage plumage patterns offer clue to dinosaur's habitat.

Nature, 551(7678):17.

RevDate: 2018-11-13
CmpDate: 2017-10-20

Liu D, Chiappe LM, Serrano F, et al (2017)

Flight aerodynamics in enantiornithines: Information from a new Chinese Early Cretaceous bird.

PloS one, 12(10):e0184637.

We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yixian Formation of eastern Inner Mongolia, China. Although morphologically similar to Cathayornithidae and other small-sized enantiornithines from China's Jehol Biota, many morphological features indicate that it represents a new species, here named Junornis houi. The new fossil displays most of its plumage including a pair of elongated, rachis-dominated tail feathers similarly present in a variety of other enantiornithines. BMNHC-PH-919 represents the first record of a Jehol enantiornithine from Inner Mongolia, thus extending the known distribution of these birds into the eastern portion of this region. Furthermore, its well-preserved skeleton and wing outline provide insight into the aerodynamic performance of enantiornithines, suggesting that these birds had evolved bounding flight-a flight mode common to passeriforms and other small living birds-as early as 125 million years ago.

RevDate: 2020-09-29

Wiemann J, Yang TR, Sander PN, et al (2017)

Dinosaur origin of egg color: oviraptors laid blue-green eggs.

PeerJ, 5:e3706.

Protoporphyrin (PP) and biliverdin (BV) give rise to the enormous diversity in avian egg coloration. Egg color serves several ecological purposes, including post-mating signaling and camouflage. Egg camouflage represents a major character of open-nesting birds which accomplish protection of their unhatched offspring against visually oriented predators by cryptic egg coloration. Cryptic coloration evolved to match the predominant shades of color found in the nesting environment. Such a selection pressure for the evolution of colored or cryptic eggs should be present in all open nesting birds and relatives. Many birds are open-nesting, but protect their eggs by continuous brooding, and thus exhibit no or minimal eggshell pigmentation. Their closest extant relatives, crocodiles, protect their eggs by burial and have unpigmented eggs. This phylogenetic pattern led to the assumption that colored eggs evolved within crown birds. The mosaic evolution of supposedly avian traits in non-avian theropod dinosaurs, however, such as the supposed evolution of partially open nesting behavior in oviraptorids, argues against this long-established theory. Using a double-checking liquid chromatography ESI-Q-TOF mass spectrometry routine, we traced the origin of colored eggs to their non-avian dinosaur ancestors by providing the first record of the avian eggshell pigments protoporphyrin and biliverdin in the eggshells of Late Cretaceous oviraptorid dinosaurs. The eggshell parataxon Macroolithus yaotunensis can be assigned to the oviraptor Heyuannia huangi based on exceptionally preserved, late developmental stage embryo remains. The analyzed eggshells are from three Late Cretaceous fluvial deposits ranging from eastern to southernmost China. Reevaluation of these taphonomic settings, and a consideration of patterns in the porosity of completely preserved eggs support an at least partially open nesting behavior for oviraptorosaurs. Such a nest arrangement corresponds with our reconstruction of blue-green eggs for oviraptors. According to the sexual signaling hypothesis, the reconstructed blue-green eggs support the origin of previously hypothesized avian paternal care in oviraptorid dinosaurs. Preserved dinosaur egg color not only pushes the current limits of the vertebrate molecular and associated soft tissue fossil record, but also provides a perspective on the potential application of this unexplored paleontological resource.

RevDate: 2018-12-02
CmpDate: 2017-10-16

Lefèvre U, Cau A, Cincotta A, et al (2017)

A new Jurassic theropod from China documents a transitional step in the macrostructure of feathers.

Die Naturwissenschaften, 104(9-10):74.

Genuine fossils with exquisitely preserved plumage from the Late Jurassic and Early Cretaceous of northeastern China have recently revealed that bird-like theropod dinosaurs had long pennaceous feathers along their hindlimbs and may have used their four wings to glide or fly. Thus, it has been postulated that early bird flight might initially have involved four wings (Xu et al. Nature 421:335-340, 2003; Hu et al. Nature 461:640-643, 2009; Han et al. Nat Commun 5:4382, 2014). Here, we describe Serikornis sungei gen. et sp. nov., a new feathered theropod from the Tiaojishan Fm (Late Jurassic) of Liaoning Province, China. Its skeletal morphology suggests a ground-dwelling ecology with no flying adaptations. Our phylogenetic analysis places Serikornis, together with other Late Jurassic paravians from China, as a basal paravians, outside the Eumaniraptora clade. The tail of Serikornis is covered proximally by filaments and distally by slender rectrices. Thin symmetrical remiges lacking barbules are attached along its forelimbs and elongate hindlimb feathers extend up to its toes, suggesting that hindlimb remiges evolved in ground-dwelling maniraptorans before being co-opted to an arboreal lifestyle or flight.

RevDate: 2018-07-20
CmpDate: 2018-07-20

Brown CM, Henderson DM, Vinther J, et al (2017)

An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics.

Current biology : CB, 27(16):2514-2521.e3.

Predator-prey dynamics are an important evolutionary driver of escalating predation mode and efficiency, and commensurate responses of prey [1-3]. Among these strategies, camouflage is important for visual concealment, with countershading the most universally observed [4-6]. Extant terrestrial herbivores free of significant predation pressure, due to large size or isolation, do not exhibit countershading. Modern predator-prey dynamics may not be directly applicable to those of the Mesozoic due to the dominance of very large, visually oriented theropod dinosaurs [7]. Despite thyreophoran dinosaurs' possessing extensive dermal armor, some of the most extreme examples of anti-predator structures [8, 9], little direct evidence of predation on these and other dinosaur megaherbivores has been documented. Here we describe a new, exquisitely three-dimensionally preserved nodosaurid ankylosaur, Borealopelta markmitchelli gen. et sp. nov., from the Early Cretaceous of Alberta, which preserves integumentary structures as organic layers, including continuous fields of epidermal scales and intact horn sheaths capping the body armor. We identify melanin in the organic residues through mass spectroscopic analyses and observe lighter pigmentation of the large parascapular spines, consistent with display, and a pattern of countershading across the body. With an estimated body mass exceeding 1,300 kg, B. markmitchelli was much larger than modern terrestrial mammals that either are countershaded or experience significant predation pressure as adults. Presence of countershading suggests predation pressure strong enough to select for concealment in this megaherbivore despite possession of massive dorsal and lateral armor, illustrating a significant dichotomy between Mesozoic predator-prey dynamics and those of modern terrestrial systems.


ESP Quick Facts

ESP Origins

In the early 1990's, Robert Robbins was a faculty member at Johns Hopkins, where he directed the informatics core of GDB — the human gene-mapping database of the international human genome project. To share papers with colleagues around the world, he set up a small paper-sharing section on his personal web page. This small project evolved into The Electronic Scholarly Publishing Project.

ESP Support

In 1995, Robbins became the VP/IT of the Fred Hutchinson Cancer Research Center in Seattle, WA. Soon after arriving in Seattle, Robbins secured funding, through the ELSI component of the US Human Genome Project, to create the original ESP.ORG web site, with the formal goal of providing free, world-wide access to the literature of classical genetics.

ESP Rationale

Although the methods of molecular biology can seem almost magical to the uninitiated, the original techniques of classical genetics are readily appreciated by one and all: cross individuals that differ in some inherited trait, collect all of the progeny, score their attributes, and propose mechanisms to explain the patterns of inheritance observed.

ESP Goal

In reading the early works of classical genetics, one is drawn, almost inexorably, into ever more complex models, until molecular explanations begin to seem both necessary and natural. At that point, the tools for understanding genome research are at hand. Assisting readers reach this point was the original goal of The Electronic Scholarly Publishing Project.

ESP Usage

Usage of the site grew rapidly and has remained high. Faculty began to use the site for their assigned readings. Other on-line publishers, ranging from The New York Times to Nature referenced ESP materials in their own publications. Nobel laureates (e.g., Joshua Lederberg) regularly used the site and even wrote to suggest changes and improvements.

ESP Content

When the site began, no journals were making their early content available in digital format. As a result, ESP was obliged to digitize classic literature before it could be made available. For many important papers — such as Mendel's original paper or the first genetic map — ESP had to produce entirely new typeset versions of the works, if they were to be available in a high-quality format.

ESP Help

Early support from the DOE component of the Human Genome Project was critically important for getting the ESP project on a firm foundation. Since that funding ended (nearly 20 years ago), the project has been operated as a purely volunteer effort. Anyone wishing to assist in these efforts should send an email to Robbins.

ESP Plans

With the development of methods for adding typeset side notes to PDF files, the ESP project now plans to add annotated versions of some classical papers to its holdings. We also plan to add new reference and pedagogical material. We have already started providing regularly updated, comprehensive bibliographies to the ESP.ORG site.

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Feathered Dinosaurs

The whole idea of feathered dinosaurs seems odd, but the fossil evidence is clear: many dinosaurs were covered in feathers well before flight had been invented. Since all modern birds are the direct living descendents of dinosaurs, the next time you watch an arrogant starling strutting in your yard, think miniature T. rex. R. Robbins

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Papers in Classical Genetics

The ESP began as an effort to share a handful of key papers from the early days of classical genetics. Now the collection has grown to include hundreds of papers, in full-text format.

Digital Books

Along with papers on classical genetics, ESP offers a collection of full-text digital books, including many works by Darwin and even a collection of poetry — Chicago Poems by Carl Sandburg.


ESP now offers a large collection of user-selected side-by-side timelines (e.g., all science vs. all other categories, or arts and culture vs. world history), designed to provide a comparative context for appreciating world events.


Biographical information about many key scientists (e.g., Walter Sutton).

Selected Bibliographies

Bibliographies on several topics of potential interest to the ESP community are automatically maintained and generated on the ESP site.

ESP Picks from Around the Web (updated 07 JUL 2018 )