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Sinosauropteryx tail "scales"



From: Ben Creisler
bcreisler@gmail.com




Checking the DML archives, it appears this paper did not get mentioned
when it appeared in pre-publication form (my bad, I guess). It's
officially published now.


Theagarten Lingham-Soliar (2013)
The evolution of the feather: scales on the tail of Sinosauropteryx
and an interpretation of the dinosaur’s opisthotonic posture.
Journal of Ornithology 154 (2): 455-463
DOI: 10.1007/s10336-012-0910-7
http://link.springer.com/article/10.1007/s10336-012-0910-7


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.