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THESCELOSAURUS AND ORNITHOPOD SYSTEMATICS
Recently, Jaime Headden posted an idea that _Thescelosaurus_ formed a clade
with _Dryosaurus- and _Tenontosaurus_. Most of the characters he cited seem
to be based on the general large size and robust nature of both
_Thescelosaurus_ and _Tenontosaurus_.
In truth though, Thescelosaurus_ and _Tenontosaurus_ differ quite a bit in the
details of their skeletons, especially their teeth. The teeth of
_Tenontosaurus_ are certainly those of a euornithopod: they have a strong
central ridge, very fine denticles, and a very wide occlusal surface.
_Tenontosaurus_ also lacks any premaxilary teeth.
Thescelosaurus_, by contrast, has teeth that are very similar in rough profile
to those of _Lesothosaurus_, having fewer, larger denticles. There are also
numerous ridges in a concentric pattern converging at the cingulum.
Additionally, _Thescelosaurus_ has 5 premaxillary teeth like most non-
If anyone is interested, here is my phyologeny of the Ornithischia, with
special emphasis on the basal Ornithopoda. It needs to be viewed in a
| +--Bugenasaura infernalis
| | | +--Othnielia rex
| | +--"Hecaicursor" multidens ("Yandusaurus"
| +--+--Zephyrosaurus schaffi
| +--Orodromeus makelai
| +--Parksosaurus warrenae
If the Pilgrims woulda had Jay Leno's chin, they coulda plowed their fields