CARNOTAURUS ARMS

[darren.naish@port.ac.uk]

On the subject of restoring _Carnotaurus_, Luis Rey writes..

> I had to do a bunch of mistaken
> reconstructions of those 'weirdest o weirdest' hands until I got 
> mine on this paper. The thumb has turned into a spike facing 
> backwards while the palm of the hands seem to be facing outwards. 
> What this animal was doing with these hands is anyody's guess... get 
> the Novas and Coria paper!!

It's Bonaparte, Novas and Coria (1990).. anyway... As the person who 
*gave* Luis his copy of the _Carnotaurus_ paper (I'm such a saint), I 
was the one who indicated that some things in his restoration were 
not quite right. 

Following Greg Paul's PDOTW restoration, just about 
everyone has been giving _Carnotaurus_ top-to-bottom flattened horns. 
This is incorrect: as you can see from the head-on photos now 
published in various glossy dino books and magazines, the carnotaur 
horns are top-to-bottom thick, rounded, and very stout. Greg's now 
updated his carnotaur to depict this morphology (see the Glut and 
Lessem encyclopedia - IMHO one of the worst dinosaur books ever 
written). I presume the error crept following the publication of 
short preliminary reports which did not figure the skull in frontal 
view.

Having read the _Carnotaurus_ paper about 10 times, I am *still* 
absolutely perplexed as to how the arms and hands really work. The 
problem is that the text and the diagram in Bonaparte, Coria and 
Novas (1990) are not in agreement. My conclusion is that the palms 
were, as is to be expected in theropods, inwards facing (some people 
who have read the paper think that the palms were _outward_ facing) 
and the manual spike (which has been compared by some with 
the_Iguanodon_ pollex) was _backward_ pointing (i.e. directed 
caudally), and homologous to digit 4. Cranially, there are 3 short 
digits. These digits are so short that someone (I don't know who) has 
suggested that they were united in a 'mitten'. You can see this in 
certain life restorations of _Carnotaurus_.

Incidentally, the new _Nature_ paper on _Sinosauropteryx_ (Chen, Dong 
and Zhen 1998) includes the mis-spelling _Carnosaurus_. Probably not 
a first.

Another problem I have with _Carnotaurus_ - though actually with 
abelisaurids in general - is the maxillary fenestra. In 
_Carnotaurus_, there is at least one (actually two) depressions 
rostral to the ant. fenestra, and within the ant. fossa (sensu 
Witmer). Bonaparte, Coria and Novas (1990) regarded the lower one of 
these as the maxillary fenestra. This is at odds with the South 
American team's convinction that abelisaurids are ceratosaurian 
because - following Gauthier (1986) - 'the maxillary fenestra is a 
character of tetanuran theropods'. The problem may have been resolved 
by Currie and Zhao (1994) - the _Sinraptor_ paper (perhaps the most 
splendid and useful piece of theropod literature yet published) - who 
are suspicious of the identification of this structure in 
_Carnotaurus_ as a max. fenestra. It looks more like a shallow 
pneumatophore: whatever, it is indistinct and not comparable to the 
very obvious max. fenestra seen in tetanurans. OK.. but, a max. 
fenestra is also reconstructed in _Abelisaurus_ by Bonaparte and 
Novas (1985), and what's known of the maxilla (as figured by them) 
seems to support this. So, if abelisaurids have a max. fenestra, then 
either this structure is more widely distributed than presently 
thought, or, god forbid (character incongruity), abelisaurids are 
tetanurans. 

Some more problems; Hu (1993) labels a structure in _Dilophosaurus 
sinensis_ as the 'second ant. fenestra': the name Osborn (1912) gave 
to the max. fenestra; _Irritator_ has a max. fenestra (so if it *is* 
a spinosaur, this supports the position of spinosaurs within the 
Tetanurae); Sereno et al. (1994) [_Afrovenator_ paper] confuse 
everything by referring to a 'promaxillary fenestra' in the 
_Afrovenator_ maxilla when there is actually no fenestra at all - 
their unifying maxillary characters of _Eustreptospndylus_ and 
_Torvosaurus_ are also problematical and don't appear, to me, to 
exist (they refer to a ventral margin of the ant. fossa in 
_Eustreptospondylus_, but it doesn't seem to have one.. in fact 
Bakker et al. (1992) used *absence* of ant. fossa's ventral margin as 
a unifying character of the same clade!); and, most recently, Sues 
(1997)  - the _Chirostenotes_ paper - says that a max. fenestra is 
'present in all other non-avian theropods except..._Erlicosaurus_'. 
Whoops - bit of an error there I think.

If this isn't worthy of a response from Tom Holtz I don't know what 
is;)

Of course, I owe my debt to Tracy. (I'll pay you at the next SVP 
meeting Tracy..)

"That name no longer holds any meaning for me"

DARREN NAISH
darren.naish@port.ac.uk