Liopleurodon vs. Eustreptospondylus (was RE: The birds vs. the pterosaurs)

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> David Marjanovic
>
> > >It reminds me of a scene from Walking With Dinosaurs, when a plesiosaur
> (or
> > >was it a mosasaur--I don't remember) reached up and captured a
> theropod.
> > >Thus, this aquatic animal was clearly at the top of the
> terrestrial food
> > >chain.  Actually, I didn't like that hypothesis at all.
>
> Neither did I. The theropod was *Allosaurus*, and the plesiosaur was
> supposed to be *Liopleurodon*, which was ONLY 12 or so and not 25
> m long as
> claimed.
>

I) The theropod was _Eustreptospondylus_, not _Allosaurus_.  (Note that the
fauna in that episode is supposed to be the Oxford Clay).
II) Although 25 m is probably a stretch, there is evidence that
_Liopleurodon_ exceeded 12 m.
III) The inspiration for this scene was, of course, the classic nature show
footage of orcas rushing up beaches to grab a pinniped for lunch, then
wiggling back into the surf.  Of course, that is done on nice sandy beaches,
not up rocky spits!

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796


> -----Original Message-----
> > I think it was some type of mosasaur, and it`s attack, (if it could have
> > happened at all), was an unusual event. Hardly what would
> qualify placing
> it
> > at the top of a terrestrial food chain.It seems that the large
> pterosaurs
> in
> > question were specifically adapted for skimming the surface,
> and catching
> > fish on a regular basis, thus qualifying their placement as top
> predators
> in
> > this particular food chain. PS,...I don`t believe a food chain has to be
> > constrained to specific physical boundaries, ie...aquatic vs
> terestrial or
> > airborn.
>
> True. BTW, I'd call azhdarchids aerial, not terrestrial, as they seem to
> have spent most of their lives hanging in the air above oceans, like
> albatrosses.
>
> > >Back to pterosaurs.  I figured the pterosaurs that survived to
> the end of
> > >the Cretaceous, which were flying eaters of fish and therefore
> dependent
> on
> > >sight for finding food, simply couldn't see anything to catch in an
> > >environment where the brightest light intensity was only a fraction of
> that
> > >of the full moon.
> >
> > Could have been. I was even going to mention this, but again, I
> think the
> > root cause of the KT extinction was the short term (couple of months)
> > depletion of the photosynthetic base of the food chain. That alone would
> > account for the extinction of some forms, and the survival of
> others. This
> > is seen as > the main cause < of the extinctions in the oceans, so why
> > should terrestrial extinctions at the K-T boundary have some other
> cause???
>
> The impact was so catastrophic that it is quite useless to look for the
> exact cause of the extinction of any group (and the fossil record will
> hardly tell months apart).
>