[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

alvarezsaurs and hypapophyses



On gnetophytes etc, Nick L asked...

Do either of these guys have any fossil record at all?

Yes, gnetophyte pollen is known from the Triassic and the Cretaceous and is apparently near-indistinguishable from that of _Ephedra_. Work on gnetophyte phylogeny indicates that _Welwitschia_ diverged during the Cretaceous I believe (the ucmp website had a good section on gnetophyte fossils but wasn't working last time I checked). If the Triassic record is valid then, as some have argued, it might be that angiosperms originated in the Triassic.

Fond as I am of Nick's suggestion that alvarezsaurids might have been
ant-eaters.. Nick, have you looked at a tarsipedid (honey possum)
skull? Obviously lacks the postcranial specialisations seen in
alvarezsaurids and extant myrmecophagous forms but the skull
morphology is superficially similar.

Haven't looked at them. To the extent that nectar feeders and myrmecophages need to extend their tongues as far as possible into tight spaces to lap up food, they should look the same, so I guess the question is how they would differ; I'm not sure. Regarding bees as a food, I'm sure it's possible, but ants and termites are more abundant in most environments and so more things specialize on them, also they have much harder nests, demanding much more specialization of the forelimbs. Then again bees will nest in logs and such.
Darren was mentioning hypapophyses a while back. I've been seeing these around a bit- a while back, I noticed some in Compsognathus and figured that might throw it in to Maniraptora, but then I noticed that some pretty damn large ones are present in a specimen of Allosaurus as well, along with Sinraptor of course so this means that character isn't particularly informative (they are even larger in e.g. alvarezsaurs, oviraptorosaurs, deinonychosaurs tho so they support these guys as a clade). Other stuff- pubic boot is also pretty long in Allosaurus and tyrannosaurids so I'm not sure about the long boot pulling Compsognathus out with Coelurus. Fan-shaped neural spines are definitely present in at least some ornithomimids. In short: Compsognathus is presumably somewhere between basal Coelurosauria and basal Maniraptora, I wouldn't want to say much else. Sinosauropteryx is a tetanuran, and until some decent photos/description come out on the larger specimen, hard to say much more than that.
-N