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Journal of Ornithology

, Volume 154, Issue 2, pp 455–463 | Cite as

The evolution of the feather: scales on the tail of Sinosauropteryx and an interpretation of the dinosaur’s opisthotonic posture

  • Theagarten Lingham-Soliar
Original Article

Abstract

The epidermis and dermis are exposed in the tail region of the theropod dinosaur Sinosauropteryx. The specimen under study, like many others of the genus and other air-breathing vertebrates discovered in the Jehol biota, shows strong opisthotonus (i.e., recurvature of the spine) that includes the neck and tail. Here, recurvature of the tail upwards is considered to have aided the separation of the dermal and epidermal elements of the skin. Addressing a somewhat controversial question, the sequence of events in which this apparently occurred also suggests that the development of opisthotonus may have occurred post mortem rather than perimortem in this specimen. Crucially, epidermal structures considered to be scales are preserved overlying the posterior part of the tail and alongside it. They are approximately 2.0–2.5 mm in diameter and have distinctive papillae radiating around a central point, comparable to scales in some modern day lizards. Some of these scales overlie thick structural fibres external to the body outline, extending posteriorly at steep angles to the body's long axis, considered by many workers to be protofeathers. Intervening between the epidermal scales and the deeper structural fibres are preserved traces of a dermal fibre meshwork with two layers of oppositely oriented fibres.

Keywords

Sinosauropteryx Epidermis Dermis Structural fibres Scales Post mortem opisthotonus 

Zusammenfassung

Die Evolution der Feder: Schuppen auf dem Schwanz von Sinosauropteryx und eine Interpretation der opisthotonischen Wirbelsäulenverkrümmung

Die Epidermis und Dermis des zu den Therapoden gehörenden Sinosauropteryx liegen in der Schwanzregion frei. Das untersuchte Exemplar zeigt, wie viele andere des Genus und andere lungenatmende Wirbeltiere der Jehol Biota, einen starken Opisthotonus, also eine Rückwärtskrümmung der Wirbelsäule einschließlich Hals und Schwanz. Wir nehmen an, dass die Rückwärtskrümmung des Schwanzes zur Trennung der dermalen und epidermalen Teile der Haut beigetragen hat. Die Abfolge der Vorgänge in der dies offenbar auftrat, legen auch nahe, dass der manchmal kontrovers diskutierte Opisthotonus eher postmortem als im Sterben auftrat. Von entscheidender Bedeutung sind epidermale Strukturen, die für Schuppen gehalten werden, die das hintere Ende des Schwanzes und dessen Seiten bedecken. Sie haben einen Durchmesser von ungefähr 2.0–2.5 mm und haben charakteristische Papillen, die um einen zentralen Punkt herum liegen, ähnlich wie bei den Schuppen von manchen rezenten Echsen. Manche dieser Schuppen liegen auf dicken strukturellen Fasern, die auf der Außenseite des Körpers im spitzen Winkel nach hinten liegen und von vielen Wissenschaftlern für Federvorläufer gehalten werden. Zwischen den epidermalen Schuppen und den tiefer liegenden strukturellen Fasern ist ein Netzwerk von dermalen Fasern mit zwei Lagen von gegenläufig orientierten Fasern erhalten.

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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2012

Authors and Affiliations

  1. 1.Biological and Conservation SciencesUniversity of KwaZulu-NatalDurbanSouth Africa

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