Turtles and dinosaur predators (Re: Oviraptorids as Parrots?)

[Phil Bigelow <bigelowp@juno.com>]

Carpenter, K., and D. Lindsey. 1980. The dentiary of Brachychampsa
montana Gilmore (Alligatorinae; Crocodylidae), a late Cretaceous
turtle-eating alligator. Journal of Paleontology, vol. 54(6):1213-1217. 

BTW:  The Hell Creek Formation contains the remains of the moderately
large (1+ meter) land tortoise _Basilemys sinuosa_ Riggs 1906.  This slow
critter should have been easy pickin's for juvie and young adult
Tyrannosaurs, but since it has a fair preservational bias in the
formation, it must have been relatively common on the Hell Creek
landscape.

To a tyrannosaur, chasing and eating a land tortoise is like a human
running-down and eating a pie that is sitting on a picnic table.  How did
these (relatively immobile) land creatures avoid predators with a bite
force of over a ton per square inch?

<pb>
--

On Sun, 05 Feb 2006 14:24:04 -0800 (PST) Jura <pristichampsus@yahoo.com>
writes:
> --- "Jaime A. Headden" <qilongia@yahoo.com> wrote:
> 
> > Jura (pristichampsus@yahoo.com) wrote:
> > 
> > <Schwimmer (2002) hypothesized that _Deinosuchus_
> > acquired it's incredible bite
> > force (18,000 N!) by originally specializing in
> > turtle eating. The rear teeth
> > are low and rounded. These are believed to be the
> > main shell crushing tools.>
> > 
> >   There are quite a few alligatorids with low and
> > rounded, or simply downright
> > bulbous posterior teeth. Most alligatorids and
> > crocodylids are opportunistic,
> > and this may reveal ancestral features in the diet,
> > but not neccessarily
> > declare the _current_ dietary regime. Note that
> > features may be exapted from an
> > originally specialized function as well as be
> > derived _for_ that function.
> 
> +++++++++++++++++++++++++++++++++++++++++++++++++
> 
> Extant alligatorids do maintain some rounded rear
> teeth. Low and behold, these are also the only extant
> crocodylians to show a dietary preference for turtles.
> 
> 
> Morphologically, turtle eaters tend to show rounded,
> separated and deeply rooted teeth. Whereas
> molluscivores (the other major shell crushers) show
> tightly spaced, flat and shallow rooted teeth.
> 
> Along with _Deinosuchus_, there were a few more
> crocodyliformes that are believed to have been...er,
> chelonivorous. _Phosphatosaurus, Brachychampsa_ and
> _Albertochampsa_ also show turtle eating dentition.
> 
> Schwimmer also mentions a few more pieces evidence,
> including the close association of various chelonian
> species with _Deinosuchus_ and (perhaps most
> compelling of all) the presence of fossilized turtle
> shells showing various bite marks and puncture wounds.
> Many of these wounds fit a _Deinosuchus_ tooth
> remarkably well.
> 
> Indeed, Schwimmer hypothesized that east coast
> _Deinosuchus_ exapted their extreme turtle crushing
> jaw morphology to a diet of dinosaurs as they headed
> out west. There are a few dinosaur bones that suggest
> _Deinosuchus_ snacked on dinosaurs, at least, every
> once in a while.
> 
> Jason
> 
> "I am impressed by the fact that we know less about many modern 
> [reptile] types than we do of many fossil groups." - Alfred S. 
> Romer
> 
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