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Re: Not dinos, but interesting, in an evolutionary sense



At 02:41 PM 5/14/99 -0500, Matt Bonnan wrote:
I will try to throw in something dinosaurian at the end to justify this.

>While internal testicles and nephrostomes are
>interesting features of elephants, how the well-developed pillar-like
>limbs and other terrestrial features would have developed from aquatic
>mammals like the dugong, or how a complex probocis would develop,
>isn't clear. I do not know all the details on elephant evolution, but
>I seem to remember hyraxes being their closest living relatives, and
>those animals have a small probocis-like nose and a permanently
>pronated hand due permanent cross-over of the radius and ulna, like in
>the elephant.

I'm not wholly convinced by the abstract in question, but some things to
clarify:

I) Sirenians, not hyraxes, are thought on morphology and molecules to be the
closest living taxon to Proboscidea.  Sirenia & Proboscidea, together with
the aquatic desmostylians and the terrestrial arsinotheres form the clade
Tethytheria.  Hyraxes are EITHER the sister taxon to Tethytheria, or the
sister taxon to Perissodactyla.

II) Also, most of the primitive proboscideans are, morphologically,
something like elongated pygmy hippos with semi-sirenian heads.  While I
would not think that _Moeritherium_ or some of the other Early Tertiary
proboscideans were out in the open seas, they have the same general body
form of other known or proposed large semi-aquatic mammals (hippos, some of
the extinct rhinoceratoids, some of the South American ungulates).

Hmmm...., now something dinosaurian.  What could it be...?

Got it:  Just saw the Portuguese _Allosaurus fragilis_ paper.  Rest assured,
it is not the same taxon as _Lourihanosaurus_.  The _Allosaurus_ has a good
old-fashioned derived obturator notch on its pubis, while _Lourihanosaurus_
has a great whopping enclosed obturator foramen.  Also, the obturator
process of the ischia are different: _Lourihanosaurus_ has a small
trapezoidal shaped one, while the Portuguese _Allosaurus_ has a large and
fairly weird shaped structure.  (I would have thought that was sufficient
grounds to put it in a different taxon than _A. fragilis_, at least, but Dan
Chure reports this condition in specimens of _Allosaurus_ which he is
presumabley retaining in _A. fragilis_.  However, it is similar to obturator
process in the no-longer-headless wonder species of _Allosaurus_, yet to be
named.

There, got some theropods into the post!

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661