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RE: Do we have dromaeosaurid evolution backward?
Tim Williams 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.
Eh, lots of carnivorous taxa have at least one character Zanno and Makovicky
identify as herbivory-related.
Decurved dentary- Masiakasaurus.
Dentary symphysis U-shaped- abelisaurids, carcharodontosaurids.
Conical anterior teeth- coelophysoids, megalosauroids, compsognathids.
Elongate anterior teeth- Daemonosaurus, Masiakasaurus, Ornitholestes.
Unserrated premaxillary teeth- coelophysids, spinosaurines, juvenile
tyrannosaurines, most basal coelurosaurs, microraptorians.
Teeth lack recurvature- spinosaurines.
Heterodont dentition- More or less developed in most theropods, but notable in
Pubic shaft anteriorly concave- some tyrannosaurids.
Pubis retroverted- Herrerasaurus, dromaeosaurids.
And that's not even mentioning carnivorous birds.
> 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.
Again, the only coding difference from compsognathids is the decurved (right)
dentary (since compsognathids are miscoded as lacking conical anterior teeth).
> > 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
And many other sauropodomorphs, where Eshanosaurus probably belongs.
Has anyone seriously suggested fruit for Masiakasaurus? Surely it's too large
to be an insectivore. Fish sure, but that's hypercarnivory.
> > 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.
I dunno, my examination of the holotype suggests the anterior teeth have a flat
lingual side. But as noted above, this isn't much of an indicator of diet.
Besides the carnivorous taxa with conical anterior teeth, you also get
herbivorous taxa with D-shaped teeth like Incisivosaurus (first pair),
Pelecanimimus and Falcarius.
> > 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
The metatarsofemoral ratio is ~57% in Ornitholestes, but Velociraptor's is 42%
(IGM 100/986). Eudromaeosaurs' in general are low, which might be another
ancestral character shared with Ornitholestes (but not basal birds,
oviraptorosaurs, troodontids, ornithomimosaurs, etc.).