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Re: a little background



On Sun, Mar 10, 2002 at 04:51:59PM -0800, Jaime A. Headden sent:
> Graydon (graydon@dsl.ca) wrote:
> >Dromaeosaurs are set up to attack *bigger* stuff; troodontids seem to
> >be crepuscular and set up to go for *smaller* stuff.  There doesn't
> >seem to be a good wolf analog (taking deer about its own size);
> >everything seem to be either lions (ganging up on same size or larger
> >animals) or foxes (taking nothing much above half its own size.)
> 
> Evidence for dromies attacking bigger things than themselves is
> supported only through circumstantial evidence in the Antlers and
> Cloverly Formations, and the association of GI 100/25 and GI 100/26, a
> *Velociraptor* and *Protoceratops* where the protoceratopian would
> only have been about 175% the mass of the dromaeosaurid. Otherwise, no
> other data can be used to support the idea that dromies were
> specialized to large prey. 

What do you call the big sickle claws?  They're way overkill for
comparably sized critters.

> Troodontids are even more problematic since you only have some anatomy
> to go off, and no actual material data to indicate what they ate, when
> they ate, etc. Diurnal owls and bats still have huge eyes, and large
> eyes are true for birds generally, not just low-level-light feeders.

Dinurnal owls and bats have huge eyes but it's a retained character from
nocturnal ancestors; all troodonits were not necessarily crepuscular but
the lineage is derived from that mode of life if the eyes are accepted
as evidence of a crepuscular lifestyle at all.

> >Also, dromaeosaurids don't seem to be faster than the small bipedal
> >herbivores; they're supposedly sprint-and-seize-and-slash types.
> 
> Yeah, dromies typically have tibiae not that much longer than their
> femora, but what's really cool is that the metatarsus is much shorter
> than expected in a sprinter. Same for oviraptorids. It seems plausible
> to suggest more ambushing-like attacks for the dromaeosaurs based on
> limb design....

I do wonder if the metatarsus is short as an asstance to power
transmission in using the sickle claws; it wouldn't apply to
oviraptorids, though.

-- 
graydon@dsl.ca   |  Hige sceal þe heardra, heorte þe cenre,
                 |  mod sceal þe mare þe ure maegen lytlað.
                 |   -- Beorhtwold, "The Battle of Maldon"