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Re: Dilophosaurus

Patti asks:

>Hey all, definitely worth the trip. VERY fascinating, but it raises a
>question that I find thought provoking.  In the words of Sam Welles
>Dilophosaurus had a manus with  4 digits, one vestigal (smallest) and
>one that apparantly was opposing.
>1st Question:  I am assuming they speculate, or know, it was opposing
>by how it attaches the the skeleton's wrist?

We know fairly well, since one specimen (UCMP 37303, a referred specimen
found near the holotype) has an articulated (partial) manus that preserves
the probable position in life quite well. See Welles (1984: 153).

>2nd Question:  If it had an opposable (digit) (which of course is
>often referred to as one reason primates were so successful
>evolutionarily) was Dilophosaurus a tool user?

Dilophosaurus is not alone among theropods, or saurischians for that
matter, in possessing a grasping manus with some opposability of digit I
(the hallux, or thumb). Many other specimens of other taxa show some
evidence of having some degree of grasping ability. The four digit manus is
characteristic of most basal theropods.

There is no evidence of tool use whatsoever; `nuff said.

Welles, S.P. 1984. _Dilophosaurus wetherilli_ (Dinosauria, Theropoda),
osteology and comparisons. Palaeontographica Abteilung A 185: 83-180.

For those that have not heard, Sam is in fair health and is getting lots of
bed rest. If you'd like to send him get well wishes, I can provide a
mailing address (just ask off-line).

                        John R. Hutchinson
                 Department of Integrative Biology
                  3060 Valley Life Sciences Bldg.
                University of California - Berkeley
                     Berkeley, CA 94720 - 3140
                      Phone:  (510) 643-2109
                      Fax:    (510) 642-1822