Re: Frenguellisaurus ischigualastensis

[Pharris Nicholas J <pharrinj@plu.edu>]

On Fri, 15 Jan 1999, Christopher Srnka wrote:

> DinosØMP wrote:
> 
> > 1)
> >         With "Allosaurus, Megalosaurus, Giganotosaurus etc.", do you want 
> > to say
> > "Tetanurids"?
> 
> Yes, but I was thinking of those three in particular. My only reference for 
> the appearance
> of the skeleton was the Dinosaur Encyclopedia, and I thought the drawing of 
> the skull
> reminded me more of Allosaurus and Giganotosaurus (both of which I have seen 
> skeletal
> mounts of) than Herrerasaurus. I was just wondering.

As well it should!  *Megalosaurus* is considerably higher up in the
theropod tree than *Herrerasaurus* is.  That said, *M* does not show a
particularly close affinity with *Allosaurus* and *Giganotosaurus*.

*Allo* is in the Allosauridae, along with *Neovenator* and a number of
questionable genera:  *Saurophaganax*, *Wyomingraptor*, *Epanterias*,
*Creosaurus*.

*Giganotosaurus* is in the Carcharodontosauridae with 
*Carcharodontosaurus* and *Acrocanthosaurus* (and apparently something new
from Argentina).

The Allosauridae and Carcharodontosauridae, along with the Sinraptoridae
(*Sinraptor*, *Yangchuanosaurus*, ?*"Szechuanosaurus"*, ?*Siamotyrannus*),
form the Allosauroidea.

The Allosauroidea and a handful of other animals (?*Afrovenator*,
?*Cryolophosaurus*, possibly spinosaurs--their ischia show features found
elsewhere only in Allosauroidea, *Afrovenator*, *Marshosaurus*, and
*Gasosaurus*) form the Carnosauria ("all organisms more closely related to
*Allosaurus* than to birds").

The Carnosauria and the Coelurosauria (compsognathids, *Ornitholestes*,
*Deltadromeus*, *Bagaraatan*, *Tyrannosaurus*, *Deinonychus*,
*Segnosaurus*, *Rahonavis*, *Gallus*, *Corvus*, etc., etc.) together form
the Avetheropoda (or Neotetanurae).

It is at this point that *Megalosaurus*, *Torvosaurus*, *Monolophosaurus*,
and others join the tree--these, along with the Avetheropoda, form the
Tetanurae ("all organisms more closely related to birds than to
*Ceratosaurus*").

So, to answer your question, no, *Megalosaurus*, *Allosaurus*, and
*Giganotosaurus* do not form a natural group, as far as we can tell.

Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(253)535-7045