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Micropachycephalosaurus hongtuyanensis & Wannanosaurus yansiensis
Richard J. Butler, Qi Zhao (In Press). The small-bodied ornithischian
dinosaurs _Micropachycephalosaurus hongtuyanensis_ and _Wannanosaurus
yansiensis_ from the Late Cretaceous of China. Cretaceous Research. Corrected
Proof, Available online 8 April 2008 doi:10.1016/j.cretres.2008.03.002
(Can't pin down the URL.)
Abstract: "The type material of the small-bodied ornithischian dinosaurs
_Micropachycephalosaurus hongtuyanensis_ and _Wannanosaurus yansiensis_ from
the Late Cretaceous of China is reviewed. _Micropachycephalosaurus_, from the
Wangshi Formation (Campanian) of Shandong Province, was originally referred to
the clade Pachycephalosauria, but some later authors have considered it a nomen
dubium. However, despite the extremely fragmentary nature of the holotype
specimen, _Micropachycephalosaurus_ can be diagnosed by the presence of
prominent grooves on the ventral surface of the centra of the posterior dorsal
vertebra. Unambiguous pachycephalosaur synapomorphies cannot be identified in
the currently available material, and we consider this taxon Cerapoda incertae
sedis. _Wannanosaurus_, from the Xiaoyan Formation (Campanian-?early
Maastrichtian) of Anhui Province, can be diagnosed by the extreme flexure of
the humerus, and is clearly referable to Pachycephalosauria on the basis of a
large number of synapomorphies. Assessment of the phylogenetic placement of
this _Wannanosaurus_ within Pachycephalosauria is complicated by the probable
juvenile nature of the holotype and paratype specimens."
Anyway, there you have it: _Wannanosaurus_ is a pachycephalosaur, and
_Micropachycephalosaurus_ *might* be one as well, but positive evidence is
lacking. For _Micropachycephalosaurus_ , the accuracy of the name appears to
be suspect, for more than one reason: the estimated length of
_Micropachycephalosaurus_ is considerably revised upward (from 50-60 cm to over
a meter - still fairly runty, but not *that* small); and the thickened skull
roof, which would probably clinch pachycephalosaurian affinities, could not be
located among the material.
Cheers
Tim
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