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[dinosaur] Ictidosauria (Synapsida) origin and relationships




Ben Creisler
bcreisler@gmail.com



A new paper:



José F. Bonaparte & A. W. Crompton (2017)
Origin and relationships of the Ictidosauria to non-mammalian cynodonts and mammals.
Historical Biology (advance online publication)
doi:  http://dx.doi.org/10.1080/08912963.2017.1329911   
http://www.tandfonline.com/doi/abs/10.1080/08912963.2017.1329911?journalCode=ghbi20


Ictidosaurian genera are allocated to two families, Tritheledontidae and Therioherpetidae. This paper provides a diagnosis for Ictidosauria. The previously named family Brasilodontidae is shown to be a junior synonym of a family, Therioherpetidae. It is concluded that Ictidosauria originated from Late Permian procynosuchid non-mammalian cynodonts rather than from Middle Triassic probainognathid non-mammalian cynodonts. The structure of the skull and jaws of a derived traversodontid Ischignathus sudamericanus from the early Late Triassic of Argentina supports an earlier view that tritylodontids are more closely related to traversodontid than probainognathid non-mammalian cynodonts. Tritylodontids should not be included in Ictidosauria, nor should they considered to be a sister group to mammaliaforms.