RE: T. Rex Dethroned as Biggest Flesh-Eating Dinosaur

[Tim Williams <twilliams_alpha@hotmail.com>]

Thomas R. Holtz, Jr. wrote:

> To be fair, they mention both a) that _Spinosaurus_ was already 
> interepreted as bigger than _T.
> rex_ back in Stromer's day, and that b) _Giganotosaurus_ was already known 
> to be bigger than _T. rex_. So it isn't the reporter's fault. Reporters 
> rarely get to write their own headlines.

As a potential fly in the ointment, the possibility has been raised that the 
type material for _S. aegyptiacus_ might come from two different theropods 
(in this case, two very big theropods) (Rauhut, 2003).  Under this 
interpretation, the cranial material represents a _Baryonyx_-like animal, 
whereas the long-spined dorsal vertebrae come from a theropod closer to 
allosaurids.  If this _Spinosaurus_-chimera idea proves to be correct (I'm 
not holding my breath), then the cranial material described by dal Sasso et 
al. (2005), including the specimen MSNM V4047, would belong to the former.  
The tall-spined vertebrae would presumably get to keep the name 
_Spinosaurus_, so the super-large theropod (represented by MSNM V4047) would 
not be _Spinosaurus_.

Having said this, the _Spinosaurus_-chimera interpretation is controversial, 
and at the moment there is no compelling evidence to split up the cranial 
material from the vertebrae.  But who knows what tomorrow (and further 
expeditions to the Sahara) may bring.

Also, also in the theropod 'big leagues' is _Deltadromeus_ (possibly a 
junior synonym of _Bahariasaurus_).  A specimen (IPHG 1912 VIII) referred to 
_Deltadromeus_ by Sereno et al. (1996) indicates a theropod 13-13.5 m long.  
This puts it on par (lengthwise, anyway) with a large specimen of 
_Giganotosaurus_ (MUCPv-95).

_Tyrannotitan_ was also pretty big; the femur of the holotype was only 
slightly shorter than that of the _Giganotosaurus_ holotype: 140 cm vs 143 
cm (Novas et al., 2005).  That's longer than the femur of the _T. rex_ 
specimen named "Sue" - but not by much.

References

dal Sasso, C., Maganuco, S., Buffetaut, E. and Mendez, M.A. (2005). New 
information
on the skull of  the enigmatic theropod _Spinosaurus_, with remarks on its 
sizes and affinities. J. Vert. Paleontol. 25: 888-896.

Novas, F.E, de Valai, S., Vickers-Rich, P. and Rich, T. (2005). A large 
Cretaceous theropod from Patagonia, Argentina, and  the evolution of 
carcharodontosaurids. Naturwissenschaften 92: 226-230.

Rauhut, O.W.M. (2003). The interrelationships and evolution of basal 
theropod dinosaurs.  Special Papers in Palaeontology 69: 1-213.

Sereno, P.C., Dutheil, D.B., Iarochene, M., Larsson, H.C.E., Lyon, G.H., 
Magwene, P.M., Sidor, C.A., Varricchio, D.J., and Wilson, J.A. (1996).  
Predatory dinosaurs from the Sahara and Late Cretaceous faunal 
differentiation. Science 272: 986-991.


Cheers

Tim