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Re: Giganotosaurus and Epanterias



Lawrence Dunn wrote:

>Here are two questions re: those sexy supercarnivores:
>
>1) Was Giganotosaurus an "overgrown" Allosaur like Carcharodontosaurus, with 
>the same slender, slashing teeth and large, long-clawed forearms?  Or was it 
>more like a Tyrannosaurid, with an apparently crushing, trauma-inducing bite 
>and vestigial forelimbs?  How do we say which of the supercarnivores was "the 
>largest" when our evidence is the remains of a few carcasses which are, in 
>fact, substantially similar in size?  Was Giganotosaurus as pea-brained as 
>Carcharodontosaurus?

Giganotosaurus seems to be very closely related to Carcharodontosaurus and
Acrocanthosaurus, so it is a bigass allosauroid.  The teeth in particular
are Carcharodontosaurus-like.  In the case of the big allosauroids, the
forearms aren't particularly huge, but they are well developed, with massive
deltapectoral crests.  Not the sort of animal you'd want to arm wrestle!

It is true that the few specimens known of the carcharodontosaurids are very
similar in size, but their elements are demonstrably larger than any known
specimen of T. rex, so it is interesting.  As to whether Carcharodontosaurus
or Giganotosaurus was the larger, the additional specimens of the latter
should help resolve it.

(Of course, "larger" refers to the very few samples known.  We have nothing
like a good population of fossils for which to get statistically significant
averages, although the total number of T. rex specimens is rising fast).

 From what I've heard, the braincase of Giganotosaurus is very similar in
most details with Carcharodontosaurus.  However, "peabrained" is a very
relative term.  It is probably more accurate to say that tyrannosaurids
inherited the larger brains common to Coelurosauria, but that this was not
recognized due to the allometric and functionally-related increase in the
trophic elements in the skull.

(Or, to eschew obfuscation, it is probably more accurates to say that
tyrannosaurid jaws and facial bones increased faster relative to brainsize
as body size increased because of allometry and because of the feeding
adaptations of the tyrant dinosaurs).

>2) Epanterias or not?  'Nuff said.

Not.

The allosaurid part of the Epanterias hypodigm is indistinguishable from
either Allosaurus proper or Saurophaganax.  The latter seems to be the valid
name for the tyrannosaur-sized allosaurid from the Morrison.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"There are some who call me...  Tim."