[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: *Oviraptor*

Dan Bensen wrote:

<My understanding is that Caudipteryx is something
like an ancestral Oviraptor (very arguably) and that
the group evolved first into the Caenagnathids, and
then into the oviraptors.>

  This is seriously arguable. The earliest occuring
oviraptorosaur which definately proves to be one is
*Caenagnathasia* from the Turoninan? Bissekty F. of
Kazakstan. This animal was described as a
caenagnathid, but several features that link it to the
caenagnathids appear to be plesiomorphies, and there
are several even more primitive features in the jaw
that would make it likely that *Caenagnathasia* is
basal to either caenagnathids or oviraptorids. This
leaves the Djadokhta-age taxa from Mongolia as the
earliest described oviraptorosaurs, and these all
appear to be oviraptorids. The first definite
caenagnathid does not occur until the Campanian of
North America, Oldman F. (Judith River F. to some,
depends on the country you're in) of Alberta, Canada.

<The caenagnathids died out (or at least, we havn't
found any) in Asia by the late Creatacous, possibly
becuase of the dessertification of that portion of the
continent, leaving the oviraptors.>

  The geology of the LK Mongolian region is so poorly
represented in the popular literature, it's amazing.
This is not an attack against dan, by the way.

  The Mongolian strata begin to become arid around the
time of the just pre-Djadokhta lithologies, in
southern Mongolian anyway, between the Turonian and
Santonian, and by Djadokhta, though estuarine systems
did persist, there were marked dunes and sand field
(though I wouldn't be drawing ergs anytime soon), and
by the late Santonian?/early Campanian Barun Goyot
stage, the aridity appears to have _dropped_ with more
lacustrine deposits than in the Djadokhta stage.
Meanwhile, the directly overlying Nemegt stage (middle
Campanian/early Maastrichtian?) was so unlike the
Barun Goyot it's ridiculous, with an apparent flora
and fauna more reminiscent of Judithian strata in
NAmer. [Gierlinksi, Jerzykiewicz, Barsbold, Osmólska,
Kielan-Jaworowska, Dashzeveg, Currie, and Dong have
all commented on this; the entries in the
_Encyclopedia of Dinosaurs_ on the above localities
and formations and the Dinosaur Distributions chapter
(Weishampel, 1990) of _Dinosauria_ all cover this
briefly, but please do read the original articles
cited therein, because that is the only way you'll get
full understanding of the lithology and sedimentology
to render the concept of the environment closely

  In fact, two oviraptorosaurian taxa, the
caenagnathid *Elmisaurus* and the oviraptorid
*"Rinchenia" mongoliensis* both occur in the Nemegt
F., along with the possible oviraptorosaur *Avimimus.*
The Hell Creek also played host to oviraptorosaurs,
including a probable species of caenagnathid based on
the "spade-like mandible" mentioned by Currie et al.
91994) and an unnamed form briefly mentioned by
Triebold and Russell (1995) from the Sandy Site, based
on a large claw and several footprints, which indicate
a probable 15 foot animal!

  The latest Cretaceous probably hosted much more than
those reported, and the small theropod niche is
horribly underrepresented in the Lauriasian Nemegt,
Edmontonian, and Hell Creek assemblages. Based on the
probable diversification of taxa from earlier and
contiguous strata, much of this was probably built up
by dromaeosaurs, oviraptorosaurs, troodontids, and
about two other unique lineages (one represented by
*Itemirus* [Nemegt], the other by *Ricardoestesia*
[Judithian, Lancian]).

<As far as feathers go, they could well have had the
display "wings" of Caudipteryx, but probably to a
lesser extent as, one, being predators, they probably
had naked lower arms just like vultures have naked
necks, and two, they had very nice display structures
in their crests, and may not have needed "wings".>

  It is not likely they had naked lower arms, as all
preserved fossils with arm-bearing integument show
that the feathers or feather-like structures extending
onto the metacarpals or even to the proximal digits.
As for crests, only three taxa appear to have had
crests, of the multitude known: "Rinchenia,"
*Oviraptor,* and whatever taxon is represented by IGM
100/42, the "big" oviraptorosaur that Paul popularized
(Barsbold, 1981, 1983, 1986, 1988...; Paul, 1988;
Webster, 1996 -- the Nat. Geo. article, with another
specimen of the same form, but about 40% smaller).

  Arm bearing display structures would not have been
bad, either.

Jaime "James" A. Headden

"Come the path that leads us to our fortune."

Qilong---is temporarily out of service.
Check back soon.
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.