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RE: Troodon v. Pectinodon




Lee Garrison wrote:

I was wondering if anyone has any thoughts regarding the taxonomic status of _Pectinodon_. Is it now considered a junior synonym of Troodon,

Neat question.

Short answer: Yes.   :-)

Long answer: This question is potentially more complicated. These days, _Pectinodon_ is invariably considered a junior synonym of _Troodon_, following Currie (1987). The type material of _Troodon formosus_ comes from the Judith River Formation, and the type specimen of _Pectinodon bakkeri_ comes from the Lance Formation. Also referred to _Troodon formosus_ are fossils from the Horseshoe Canyon Formation and Judith River Group of Alberta, and (as you said) the Hell Creek Formation.

The thing is, because the type material of _Troodon_ is a single tooth, the referral of numerous other specimens to _Troodon_ (including the type specimens of _Stenonychosaurus_, _Polyodontosaurus_ and _Pectinodon_) depends upon this particular tooth morphology being limited to a single genus and species. However, if it is demonstrated that the _Troodon_ tooth morphology is shared by more than one species, then _Troodon_ would be a nomen dubium - as happened with _Deinodon_ and _Trachodon_ (both also from the JRF). If this were to happen, _Pectinodon_, which is also based on teeth, would also be a nomen dubium; whereas _Stenonychosaurus_ would probably launch a comeback.

But this hasn't happened yet. So _Troodon_ is safe, for the time being. Thus, _Pectinodon_ is a junior synonym of _Troodon_.

Reference

Currie, P. J. (1987). Bird-like characteristics of the jaws and teeth of troodontid theropods (Dinosauria, Saurischia). J. Vert. Paleontol. 7: 72-81.

Cheers

Tim