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Re: Do we have dromaeosaurid evolution backward?
Mickey Mortimer <firstname.lastname@example.org> wrote:
> Not to contradict you here ;) , but Zanno and Makovicky actually left
> Ornitholestes unassigned, as they said its diet was inconclusive.
To me, the fact that _Ornitholestes_ didn't fall in with the
predominantly predatory theropods is itself interesting.
I guess I interpreted Zanno and Makovicky's statement a little
differently: "Intermediate numbers of CHTs in these taxa may indicate
omnivory or dietary specializations not manifest widely in other
coelurosaurians (e.g., insectivory)." Clearly _Ornitholestes_ could
not be assigned to the same trophic category as compsognathids,
tyrannosaurids and dromaeosaurids.
> The only "herbivorous" characters it is coded as having are-
> 1. Decurved dentary. Not obviously true in the left mandible, this is also
> found in Masiakasaurus, Coelurus and many (probably insectiviorous or
> piscivorous) Mesozoic birds.
Also in _Eshanosaurus_, a likely herbivore. The diet of
_Masiakasaurus_ has been the subject of much speculation: fruit, fish,
insects? As for _Coelurus_, the dentary is the only cranial material
known for this genus, and this element is extremely slender and
> 2. Ischium longer than 66% pubic length. This is the basic arrangement for
> theropods... er... archosaurs... er amniotes. So this is present in
> carnosaurs, tyrannosauroids, megalosauroids, ceratosaurs, etc.. Not a
> herbivory-related character at all.
Yeah, that one's a wash.
> Given the fairly large, recurved teeth and generally
> carnosaurian-tyrannosauroid nature of the taxon, I would doubt if
> Ornitholestes had more plants in its diet than modern coyotes and such.
I also thought that the teeth of _Ornitholestes_ were rather conical,
especially the premaxillary teeth. Am I mistaken here? This
appraisal of _Ornitholestes_ dentition comes from Paul (1988). I
disagree with GSP's "neoflightless" hypothesis, but surely I can trust
him when it comes to determining the shape of a theropod's teeth.
> The "rather weak cursorial abilities" are based on a tibia which seemingly
> doesn't exist. I'd like to know what happened to whatever bone Osborn
> identified as a tibia.
Actually, I wasn't thinking of the phantom tibia at all. The
metatarsus of _Ornitholestes_ is only about half the length of the
femur. Even compsognathids and archaeopterygids had longer metatarsi
(~ three-quarters the length of the femur). The mt/femur ratio of
_Ornitholestes_ is about the same as that of the basal therizinosaur