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Majungatholus as cannibal



Hello,

Scott Sampson requested that I forward the following message to the list, so as 
requested:


----- Forwarded message from ssampson@umnh.utah.edu -----
Date: Fri, 25 Jul 2003 14:37:40 -0600 (MDT)
From: ssampson@umnh.utah.edu
Reply-To: ssampson@umnh.utah.edu
Subject: Majungatholus as cannibal
To: dinosaur@usc.edu

Folks,

I do not particularly desire to re-start an old thread, but I do want to clear
up a matter discussed on this list earlier in the year.  In early April, Jaime
Headden submitted a couple of messages arguing for the presence of two large
theropod dinosaurs in the Late Cretaceous (Maastrichtian) Maevarano Formation
of Madagascar.  These messages were in response to a paper by Rogers et al.,
published in Nature (vol 422(3): 515-518), postulating cannibalistic behavior
in Majungatholus.  In addition to multiple examples of tooth-marked theropod
bone, this hypothesis is based (in part) on the fact that, to date, there is
no evidence of more than one coeval mid- to large-sized theropod in this
fauna.

Jaime Headden?s argument for a second taxon was based on a partial right
dentary described by Lavocat in 1955 and assigned to Majungasaurus
crenatissimus.  Headden argued that this dentary differs in several distinct
features from materials assigned to Majungatholus.  To quote him directly, ??
the uncatalogued type of *M. crenatissimus* shows a strong dorsal curvature of
the ventral margin eminiscent of *Carnotaurus*, whereas that of the UA
material is relatively straighter; the type of *M. crenatissimus* also bears a
distinct dorsal emargination of the lateral groove, but no ventral embayment,
whereas the opposite is true of both *Carnotaurus* and the UA
material. There is a broader ventral dental shelf than is found in the UA
material, and the jaw lacks the vertical fluting of the external surface as is
found in *Aucasaurus*, *Carnotaurus* and the UA material. The jaws also show a
general taper in the posterior third to half that, if continued forward, are
similar to *Aucasaurus*, but do not occur in the UA material in which the
dentary is much more consistently deep along its length, and where the UA
material has a distinct chin, neither the *M. crenatissimus* jaw nor
*Carnotarus* do.

I am currently in the midst of writing a detailed description of the skull of
Majungatholus, co-authored with Larry Witmer (Ohio University).  This paper
will be part of an edited monograph dedicated to various aspects of the
anatomy and biology of Majungatholus.  In addition to the complete skull (FMNH
PR 2100) my colleagues and I described in 1998 (Science, 280: 1048-1051), I
have on my desk an excellent cast of the (unnumbered) Lavocat dentary, kindly
sent to me a few years back by Phillipe Taquet of the Natural History Museum
in Paris.  As stated in the 1998 paper, I do not see any significant
differences between the Lavocat specimen and FMNH PR 2100, figured in the
Science paper.  Indeed (at least to my eyes), other than size (the Paris
specimen is about 25% smaller), they are virtually identical, right down to
curvature, lateral groove morphology, surface texture, and even tooth number
(17).  The fragmentary nature of the Paris specimen, perhaps combined with
distortions associated with the published photographs, might suggest features
such as a greater degree of curvature along the ventral margin.  But a side by
side comparison shows the specimens to be all but indistinguishable from each
other.

In short, there is currently evidence for only one larger-bodied theropod from
the Late Cretaceous Maevarano Formation of Madagascar ?Majungatholus atopus.
Thus the hypothesis of cannibalism is remains robust.

Cheers,

Scott Sampson


__________________________________

Scott D. Sampson, PhD
Curator of Vertebrate Paleontology
Associate Professor of Geology and Geophysics
Utah Museum of Natural History
University of Utah
1390 East Presidents Circle
Salt Lake City, UT 84112-0050

Phone: (801) 585-0561
Fax: (801) 585-3684
Email: ssampson@umnh.utah.edu
http://www.umnh.utah.edu

----- End forwarded message -----



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miracle. The other is as though everything is a miracle.\"
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\"Men are not disturbed by things, but the view they take of things.\"
-Epictetus (55-135 A.D.)

Lindsay E. Zanno
Vertebrate Paleontology
Department of Geology and Geophysics
Utah Museum of Natural History
University of Utah
1390 E. Presidents Circle
SLC, UT 84112-0050
(801)587-9324