Re: rampant speculation

["David Marjanovic" <david.marjanovic@gmx.at>]

> And, if I could speak for Justin for a moment, I think that he is not only
noting the decline of small-medium ornithopods, but also the rise in
diversity of coelurosaurs.  So, he formulated a hypothesis to take both of
these observations into account.

:-)

> [...]  I have serious doubts that many coelurosaurs were herbivorous,

So have I: Ornithomimosaurs have moa-like skulls, according to PDW, plus
gastroliths, but there are isotopic studies (mentioned onlist whenever) that
they were omni- to carnivorous; oviraptorosaurs look like they had crushed
something -- overdesigned for eggs, underdesigned for clams, and plenty of
water snails in AFAIK the Nemegt Formation... and oviraptorosaur brooding
colonies like those of waterfowl...

> and if they were, I question whether they could pose a threat to
small-medium ornithopods.  Good hypothesis, though, and something that is
difficult to disprove.

But it assumes that coelurosaurs evolved herbivory in a world full of
already herbivorous ornithopods which, at the beginning, must have been
better adapted to that. Such things don't happen (competitive exclusion).
The only possibility is that herbivorous coelurosaurs evolved somewhere
where there were no ornithopods -- very difficult to disprove if "somewhere"
was, say, an island.
        All this is ignoring the obviously herbivorous coelurosaurs, the
segnosaurs. Well, they seem to have occupied quite a different niche (when
the ground sloths and chalicotheres died out that niche became empty and has
remained so, it seems) from any ornithopods, and if the famous Lufeng jaw is
really from a segnosaur, then they may have evolved directly after the Tr-J
mass extinction in an empty world. Now _this_ is difficult to disprove...