Filamentous Integumentary Structures Research Articles

WITHDRAWN: A maned theropod dinosaur from Gondwana with elaborate integumentary structures

Abstract Discoveries of dinosaurs with integumentary structures over the last few decades have revolutionised our understanding of the phylogenetic relationships between birds and dinosaurs as well as the origin and evolution of feathers. A remarkable number of dinosaurs have been discovered with a diverse range of preserved integumentary structures. Several of these dinosaurs are adorned with elaborate integumentary structures that have been linked to behaviours including thermoregulation, egg incubation, and sexual display. Among Theropoda, such elaborate structures have only been previously recorded within Maniraptoriformes. However, elaborate monofilamentous structures are also present in some small ornithischians. The majority of theropods preserving integumental structures come from the Upper Jurassic and Lower Cretaceous of China or the Upper Jurassic of southern Germany, and all are of Laurasian origin. Herein, we describe a new genus and species of compsognathid theropod from the Lower Cretaceous (Aptian) Crato Formation of Northeast Brazil, representing the first Gondwanan non-avian theropod with preserved filamentous integumentary structures. It is also the first non-maniraptoran possessing elaborate integumentary structures that were most likely used for display. These include slender monofilaments associated with the base of the neck, increasing in length along the dorsal thoracic region where they form an impressive mane, as well as a pair of elongate, ribbon-like structures likely emerging from the shoulder. Such elaborate integumentary structures are hitherto unknown in any other dinosaur, although superficially similar elongate display feathers emerge from the carpal region of the male standardwing bird-of-paradise (Semioptera wallacii).

Structure and homology ofPsittacosaurustail bristles

AbstractWe examined bristle‐like appendages on the tail of the Early Cretaceous basal ceratopsian dinosaurPsittacosauruswith laser‐stimulated fluorescence imaging. Our study reveals previously unknown details of these structures and confirms their identification as integumentary appendages. For the first time, we show that most bristles appear to be arranged in bundles and that they exhibit a pulp that widens towards the bristle base. We consider it likely that the psittacosaur bristles are structurally and developmentally homologous to similar filamentous appendages of other dinosaurs, namely the basal heterodontosauridTianyulongand the basal therizinosauroid theropodBeipiaosaurus, and attribute the greater robustness of the bristles ofPsittacosaurusto a higher degree of cornification and calcification of its integument (both skin and bristles). Although the psittacosaur bristles are probably homologous with avian feathers in their origin from discrete cell populations, it is uncertain whether they developed from a follicle, one of the developmental hallmarks of true feathers. In particular, we note a striking resemblance between the psittacosaur bristles and the cornified spine on the head of the horned screamer,Anhima cornuta, an extant anseriform bird. Similar, albeit thinner keratinous filaments of extant birds are the ‘beard’ of the turkey,Meleagris gallopavo, and the crown of the Congo peafowl,Afropavo congensis. All of these structures of extant birds are distinct from true feathers, and because at least the turkey beard does not develop from follicles, detailed future studies of their development would be invaluable towards deepening our understanding of dinosaur filamentous integumentary structures.

An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures

Ornithischia is one of the two major groups of dinosaurs, with heterodontosauridae as one of its major clades. Heterodontosauridae is characterized by small, gracile bodies and a problematic phylogenetic position. Recent phylogenetic work indicates that it represents the most basal group of all well-known ornithischians. Previous heterodontosaurid records are mainly from the Early Jurassic period (205-190 million years ago) of Africa. Here we report a new heterodontosaurid, Tianyulong confuciusi gen. et sp. nov., from the Early Cretaceous period (144-99 million years ago) of western Liaoning Province, China. Tianyulong extends the geographical distribution of heterodontosaurids to Asia and confirms the clade's previously questionable temporal range extension into the Early Cretaceous period. More surprisingly, Tianyulong bears long, singular and unbranched filamentous integumentary (outer skin) structures. This represents the first confirmed report, to our knowledge, of filamentous integumentary structures in an ornithischian dinosaur.

Evolution of birds: ichthyosaur integumental fibers conform to dromaeosaur protofeathers.

Filamentous integumentary structures have been reported as protofeathers in dromaeosaurs (non-avian dinosaurs). This hypothesis is considered against data on the complex architecture of dermal and subdermal collagenous fibers widely prevalent in living and extinct animals. Ichthyosaur integumental fibers, as dromaeosaur "protofeathers", are the most external structures preserved. Marked similarities are shown in branching patterns of these fibers compared with those of the dromaeosaur Sinornithosaurus; hence distinguishing between aberrant and primary features is difficult. Analysis of a pterosaur specimen shows that bent and straight fibers on the wings have functional implications. The fibers conform to the twofold shape of collagen and contradict the notion that bent integumental structures in the dinosaur Sinosauropteryx indicate softness and pliability. A suggestion also concerning Sinosauropteryx is that integumental structures with darker edges, compared with the middle, imply that they were hollow. Investigation of a similar condition in an ichthyosaur shows that it is more likely a consequence of mineralization. Dermal collagen fibers in, for example, sharks, dolphins, snakes, and turtles are shown to be grouped in bundles of varying sizes. Degradation of the dermis results in the breakdown of the fiber bundles and formation of myriad patterns of the disrupted fibers, as noted in decomposed dolphin skin. The overall findings of the study are that the thesis of dinosaur "protofeathers" requires more substantial support than exists at present.

A therizinosauroid dinosaur with integumentary structures from China

Therizinosauroidea (‘segnosaurs’) are little-known group of Asian dinosaurs with an unusual combination of features that, until recently, obscured their evolutionary relationships. Suggested affinities include Ornithischia1, Sauropodomorpha2,3, Theropoda4,5,6,7,8,9,10,11 and Saurischia sedis mutabilis12. Here we describe a new therizinosauroid from the Yixian Formation (Early Cretaceous, Liaoning, China)13. This new taxon provides fresh evidence that therizinosauroids are nested within the coelurosaurian theropods8,9,10,11. Our analysis suggests that several specialized therizinosauroid characters, such as the Sauropodomorpha-like tetradactyl pes1,2, evolved independently within this group. Most interestingly, this new dinosaur has integumentary filaments as in Sinosauropteryx14,15. This indicates that such feather-like structures may have a broad distribution among non-avian theropods, and supports the hypothesis that the filamentous integumentary structures may be homologous to the feathers of birds14,15.