Re: Morrison Sauropods\etc. (long)

[Justin Tweet <thescelosaurus@juno.com>]

On Tue, 03 Jul 2001 22:29:00 -0400 Darryl Jones <dinoguy@sympatico.ca>
writes:

[snip]
> I think we will see a lot of species being sunk in the future
(especially
> in China) as more work gets done on these dinosaurs.  They seem to
> be on the same kind of naming frenzy that North Americans were at the
turn
> of the 20th Century.  People are still sorting that mess out.  I still
> think there are a LOT of questionable species and even a few genera.

I agree with you; I confess that I've been having a lot of trouble
following the taxonomy of Chinese sauropods.

> >         The well-supported genera and species have morphological
> > differences that indicate different niches.  Of the Big Six
(*Apatosaurus*, *Barosaurus*, *Brachiosaurus*,
> >  *Camarasaurus*, *Diplodocus*, and *Haplocanthosaurus*), each is very
distinctive.  For
> > example, in feeding:
> >         *Apatosaurus* has peg-like teeth but relatively the shortest
neck and stoutest build of the Morrison
> >  diplodocids [...]
>
> These kind of make sense to me, because three are rare and the others
do seem very different in their strategies
> (Apato, Camara, and Diplo).  Having stood next to the three more common
ones, however, still leaves me wondering
> how these animals would have gotten enough to eat.  Obviously they did,
since I was able to stand next to them.  I
> cannot argue that these should be sunk, all are well enough represented
and definitely different.  However:
>
> >         Of the less common genera, we have the super-elongated
*Seismosaurus* and *Supersaurus*, mysterious
> > *Dystrophaeus*, apatosaur-like *Eobrontosaurus*, *Amphicoelias*,
*Dystylosaurus*, and titanosaurid-like
> > "Apatosaurus" *minimus* (and possibly *Dyslocosaurus* as well).
These in turn are also all distinctive.
>
> This was what I was talking about with sauropods wandering into an
ecosystem.  Either that or they were very rare.  I > wonder if some of
these will not be sunk in the future with better finds.  I am sure some
will remain dubious due to
> the fact that they are odd-ball material.  I have also heard that
Amphicoelias is likely not valid.  The "distinct femur"
> has been showing up attached to Diplodocus specimens and maybe the
neural arch was pathological.  It is so hard
> to take pathological material out of the mix.  I am sure it would kill
many genera and species of dinosaur.

        Of course, some are more distinctive than others.  Having all those
super-diplodocids at the end of the Morrison is a bit suspicious
(*Seismosaurus*, *Supersaurus*, the type of *Amphicoelias*...), and I've
wondered if some of these may just be specific variants on another genus.
 It's entirely plausible that some of the oddballs may be immigrants.
Even with that, though, we've still got three common genera and three
more less common but still important genera.  The productivity of the
Morrison must have been tremendous.

> >         This is not like *Triceratops* taxonomy...The faunal list
doesn't tell the whole story.
>
> No, you are right, but what is not clear to me (and other lay people)
is where in the time continuum these suckers
> existed.  I think that would help sort out some of my headache.

I'd like to see that as well (it's probably been published somewhere, but
I just don't know about it).

[snip]
> >         The theropods also separate well by size.  At the top we have
*Torvosaurus* and the "super" allosaurs; next is
> > regular *Allosaurus fragilis*, followed by *Ceratosaurus*, then
*Marshosaurus*. *Stokesosaurus* and the
> > "coelurosaurs" (*Ornitholestes*, *Coelurus*, *Koparion*,
*Palaeopteryx*, unidentified animals, etcetera) brought
> > up the rear.  It's not as though they were all competing for the same
food source.
>
> I can see having to many predators since we have so much prey, but even
then, there are at least three predators
> over 6 meters in most areas.  These are GIANT predators.  Luckily they
have giant prey, but there is still something
> unusual about having so many different large predators.  You are not
counting Bakker et al's megalosaurs, which
> would bring the number of giants higher.
[snip]

        True; I don't buy *Edmarka*, for example, as being significantly
different from *Torvosaurus*.  There's a handful of others too; I didn't
give a lot of space to the two new *Ceratosaurus* species; they would fit
in from about *Allosaurus fragilis* size back to *Ceratosaurus*.  There's
also "Elaphrosaurus philtippetorum", but offhand I don't know where it
would have plotted (especially since it's only based on one bone).
        Just as in the common sauropods, I'd think that the large theropods were
probably separated by their morphologies; *Ceratosaurus*, *Torvosaurus*,
and *Allosaurus* each appear to hail from widely-differing branches of
the theropod family tree, and have different skull designs and limb
proportions and builds, which were probably best suited to dealing with
certain prey animals.   Just what they were, of course, we will never
know for certain.  With all the large sauropods, ornithopods, and
stegosaurians around, there was plenty of room for
specialization.-*Thescelosaurus*

[snip]
> Darryl Jones  <dinoguy@sympatico.ca>
>
> For information on tyrannosaurids and
> cool activities and information for kids,
> visit my webpage at:
>
> http://www3.sympatico.ca/dinoguy/
>

---------------------------------------------------------------
Justin Tweet, *Thescelosaurus*
See "Thescelosaurus!": http://personal2.stthomas.edu/jstweet/index.htm

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