BEAKS, CASQUES & KINESIS

[darren.naish@port.ac.uk]

A few comments on Nick's recent post. Nick wrote...

> In some [birds], e.g. hornbills, bony contribution to a horn structure 
> (the casque) may be fairly minimal.   

I have seen sectioned hornbill skulls and recall that, in those with 
a casque, a hollow bony crest does take up much of the casque's 
internal volume. I also have photos of rhino hornbill (_Buceros 
rhinoceros_) skulls: in the skull, the crest is pretty much the same 
shape as is the casque in the live bird. I suppose this may not the 
case for all species though. Cassowaries certainly have casques where 
the bony core is small compared to the whole structure: in the two 
larger species the casque itself may be three or four times taller 
than the bony crest. The bony crest is also very fragile, in contrast 
to its horny sheath.

Nick also drew attention to possible analogy between dicynodonts and 
oviraptorosaurs. WRT this, I think it's interesting that Sues and 
Reisz (1998) suggested that some dicynodonts could have been 
omnivores or carnivores: that they are beaked and relatively 
graviportal does not prove that they were herbivores.

Incidentally, for those of you at the Oviraptorosaur Synapomorphy 
Mini-Symposium in Denver last year (Adams Mark Hotel), I have learnt 
that the David Smith who wrote the oviraptorosaur jaw motion paper IS 
the same David Smith who has recently been publishing on 
the systematics of _Allosaurus_ (J. Kirkland, pers. comm. 2000).

> (I recall one of the black hills guys arguing at 
> Dinofest that even Rex has pretty decent kinesis in a lot of 
> joints).

In her work on finite element analysis and stress distribution in 
theropod skulls, Emily Rayfield has proposed that _Tyrannosaurus rex_ 
had kinetic zones at the postorbital-jugal suture and elsewhere 
(data presented at Progressive Palaeontology 1999, Bristol Univ.).

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
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