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Re: Giganotosaurus and Epanterias



In a message dated 96-08-08 05:51:48 EDT, Thomas_R_HOLTZ@umail.umd.edu (th81)
writes:

> 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!

I had to go to Toronto a couple of weeks ago (miserable trip, by the way--the
place was hot and crowded, with constant stop-go traffic and absolutely no
places to park) and stopped in at the ROM for a few minutes. They have a cast
of an _Afrovenator_ skull on display. I checked out the teeth, and they're
quite different from the teeth of _Allosaurus_: very bladelike, laterally
compressed. Like _Carcharodontosaurus_ teeth, specifically. The rest of the
skull seems to have more in common with Big C than with _Allosaurus_ and the
sinraptorids, too. So on this feeble and superficial basis, I'd tentatively
classify _Afrovenator_ with Big C and Big G in Carcharodontosauridae. It's
quite a bit smaller than Big C and Big G; maybe I should call it Little A.

Incidentally, decades ago Friedrich von Huene (1956, maybe earlier) noted the
gigantic size of _Carcharodontosaurus_, _Bahariasaurus_, and _Spinosaurus_
("grosser als _Tyrannosaurus_!"), based on the sparse remains then known, but
nobody seems to have listened.
 
>  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).

Likewise with the forelimbs. Tyrannosaurid body size increased way faster
than the forelimbs and left them far behind.
 
>> 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.

_Epanterias_ is indistinguishable from _Allosaurus_ morphologically, but it
is distinguishable from _Saurophaganax_, which has those little processes on
the cervicals that _Epanterias_ and _Allosaurus_ lack. Big E seems to be
based on very large _Allosaurus_ individuals and is thus likely a junior
synonym, but Big S is probably a valid genus. _Saurophagus_ (the "other big
S") is based on large limb elements that aren't diagnostic and cannot be
distinguished from any referred to either Big E, big _Allosaurus_, or Big S.
So _Saurophagus_ is a _nomen dubium_ (and still a preoccupied generic name).