Feather-like development of Triassic diapsid skin appendages
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Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquama’s appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument.
KeywordsFossilized integument Skin appendage Feather evo-devo Longisquama
This work was supported by the German Research Foundation (DFG II - VO 1466/1–1) and by the Society of Vertebrate Paleontology (Patterson Memorial Grant to JF). We are thankful to Evgenii N. Kurochkin and Vladimir R. Alifanov for access to the type material in Moscow in February 2007, to Susan Turner and Jörg W. Schneider for suggestions and comments, and to Ilja Kogan for his help with the translation of Russian publications and reports.
- Haubold H, Buffetaut E (1987) A new interpretation of Longisquama insignis, an enigmatic reptile from the upper triassic of Central Asia. C R Acad Sci Ser 2 305:65–70Google Scholar
- Ji Q, Yuan C (2002) Discovery of two kinds of protofeathered pterosaurs in the Mesozoic Daohugou Biota in the Ningcheng Region and its stratigraphic and biologic significances. Geol Rev 48:221–224Google Scholar
- Lucas AM, Stettenheim PR (1972) Avian anatomy: integument. US Dept. Agriculture, Washington, DCGoogle Scholar
- Martin LD (2004) A basal archosaurian origin of birds. Acta Zool Sin 50:978–990Google Scholar
- Schaller S (1985) Wing evolution. In: Hecht MK, Ostrom JH, Viohl G, Wellnhofer P (eds) The beginnings of birds. Freunde des Jura-Museums, Eichstätt, pp 333–348Google Scholar
- Schaumberg G, Unwin DM, Brandt S (2007) New information on the anatomy of the late Permian gliding reptile Coelurosauravus. Palaeont Z 81:160–173Google Scholar
- Sharov AG (1970) A specific reptile from the Lower Triassic of Fergana. Paleontol Z 1970:127–130 (in Russian)Google Scholar
- Unwin DM, Benton MJ (2001) Longisquama fossil and feather morphology. Science 291:1900–1901Google Scholar
- Unwin DM, Alifanov VR, Benton MJ (2000) Enigmatic small reptiles from the middle-late Triassic of Kirgizstan. In: Benton MJ, Shishkin MA, Unwin DM, Kurochkin EN (eds) The age of dinosaurs in Russia and Mongolia. Cambridge University Press, Cambridge, pp 177–186Google Scholar