Heterodontosaurids (was RE: Journal of Paleontology Papers)

[Tim Williams <twilliams_alpha@hotmail.com>]

Lukas Panzarin wrote:

> If I'm not wrong, possible heterodontosaurids come from Portugal 
> (Trimucrodon cuneatus),

On this topic, I'm more likely to be wrong than you are.  :-)  Though I do 
have _Trimucrodon_ categorized as Ornithischia incertae sedis.

> and Argentina (unnamed early Carnian form, Báez et al. 1998, 2001).

Thanks - that's the one I'd forgotten (see below).

> The United States form could be a late Jurassic heterodontosaurid related 
> to Echinodon becklesii (Galton, 2002).

This is from an SVP 2002 Abstract, isn't it?  This is based on cranial 
material from the Morrison Formation of Fruita, Colorado.  I don't think 
this North American _Echinodon_ has been described in print yet, and the 
specimen may be in private hands (I'm not sure).

There is also a report of an earlier North American heterodontosaurid, from 
the Kayenta Formation - but I don't have the citation.

References

Baez, A. and Marsicano, C.A. (2001).  A heterodontosaurid ornithischian 
dinosaur from the Upper Triassic of Patagonia.  Ameghiniana 38: 271 -279.

Abstract: Fragmentary remains of a new heterodontosaurid species, comparable 
to _Heterodontosaurus_ Crompton and Charig, were discovered in concretions 
in the Laguna Colorada Formation, a Late Triassic continental sequence in 
Santa CruzProvince, Argentina.  The material consists of a weathered, left 
posterior maxillary fragment with dentition, and, tentatively, an isolated 
caniniformwith anterior and posterior serrations.  The preserved three 
maxillary teeth bear flat wear facets, and are columnar and closely packed.  
The anterior and posterior surfaces of the crowns are in contact, a feature 
considered asynapomorphy of _Heterodontosaurus_ and _Lycorhinus_ from the 
Early Jurassic upper Stormberg Group of southern Africa.  As in 
_Heterodontosaurus tucki_ Crompton and Charig, the maxillary teeth lack a 
cingulum or a constriction separating crown and root, and the wear facets of 
adjoining teeth form a single, continuous surface.  However, the posterior 
maxillary teeth bear more numerous and narrower ridges on their labial 
surfaces than those of _H. tucki_.  This new record of a heterodontosaurid 
extends the temporal range of this group of small ornithischians and, 
considering the phylogeny of ornithischians as now understood, indicates an 
extensive phyletic diversification of these dinosaurs in the Late Triassic.

Cheers

Tim