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Taxonomic status of Typothorax and Episcoposaurus (Aetosauria)



From: Ben Creisler
bcreisler@gmail.com


A new online paper:

William G. Parker (2013)
Redescription and taxonomic status of specimens of Episcoposaurus and
Typothorax, the earliest known aetosaurs (Archosauria: Suchia) from
the Upper Triassic of western North America, and the problem of proxy
“holotypes”.
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000212
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9015636&fulltextType=RA&fileId=S1755691013000212



Historic type and referred material of the aetosaurian taxa Typothorax
coccinarum, Episcoposaurus horridus and Episcoposaurus haplocerus are
redescribed and the non-aetosaurian material identified and removed, a
task previously considered “hopeless”. Reexamination of the original
material reveals that the holotypes of E. haplocerus and probably T.
coccinarum are not diagnosable at the species level and therefore are
nomena dubia. The next available names for material referred to these
taxa are Desmatosuchus spurensis and E. horridus respectively,
although it may be more desirable for reasons of taxonomic stability
to attempt to petition for a neotype in the latter case. The
redescription of historical specimens is necessary to determine their
nomenclatural validity. The use of referred specimens as proxy “type”
specimens is problematic, as these referrals were originally made not
on the basis of apomorphies, but rather on biostratigraphic and/or
geographical assumptions which are inherently circular and cannot be
unambiguously supported.