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Heterodontosaurids (was RE: Journal of Paleontology Papers)



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