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Cranial anatomy of Chinese placodonts



Ben Creisler
bcreisler@gmail.com


A new online paper:

James M. Neenan, Chun Li, Olivier Rieppel and Torsten M. Scheyer (2015)
The cranial anatomy of Chinese placodonts and the phylogeny of
Placodontia (Diapsida: Sauropterygia).
Zoological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/zoj.12277
http://onlinelibrary.wiley.com/doi/10.1111/zoj.12277/abstract


Placodonts are Triassic marine reptiles that inhabited the eastern and
western margins of the Tethys Ocean (modern South China and
Europe/Middle East). Although the crania of European taxa are
relatively well understood, those of Chinese taxa have not been
extensively studied, and most of them have not been incorporated into
a comprehensive phylogeny. Here we present the first reconstructions
of all known Chinese placodont holotype skulls using micro-computed
tomographic (μCT) scanning and/or detailed anatomical study. We also
present the first phylogenetic analyses that incorporate all placodont
genera using a general diapsid matrix that includes postcranial
characters, and a placodont-only cranial matrix. Results vary between
the matrices; however, both support a monophyletic Placodontia with
eastern taxa interspaced throughout, indicating no major separation
between the eastern and western Tethyan realms. Support is strong for
a western Tethyan origin of Placodontia, although the highly nested
Placochelyidae first appear in the upper Middle Triassic of the
eastern Tethys. Thus, all placodont clades appear to have originated
in a period of intense speciation during the Middle Triassic.