RE: SLC loss (was: Re: Revising Hou et al, 96) & Burian

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Luc Bailly wrote:

> Does it mean that they were able again, for example, to catch a prey
> with ONE hand?

The thing is, of the total Maniraptora (despite the name), very few groups
appear to be specialized for catching or consuming prey at all.

Oviraptorosaurs may have been omnivores.  It's been suggested that the jaws
might have beens specialized for eating eggs, or shellfish, or for cracking
open bones.  In any case, they probably weren't hypercarnivores.

_Caudipteryx_ - the skull doesn't look equipped for a carnivorous diet, and
there are gastroliths associated with the skeleton.  (Gastroliths suggests
plant- or insect-eating... though I understand at least one allosaur [from
Portugal] has them too.)

Therizinosaurs - ponderous plant-eaters, no doubt about that.

Alvarezsaurs - the highly transformed forelimbs were unsuitable for grasping
anything, and may have been used for digging up tubers, tearing up nests or
hives, or stripping bark.  Certainly not predators.

Troodontids - the sickle-claw (lost in _Borogovia_) suggests raptorial
habits, but those teeth... maybe omnivorous, though the sickle-claw would
come in handy for the flesh component of its diet.

Dromaeosaurids - 100% predator.  Among maniraptorans, dromies are actually
exceptional in this respect.

The SLC appears to have evolved in small coelurosaurs that had a heterodont
dentition, which suggests a generalized diet of small prey items - insects,
worms, small vertebrates...  Primitive eumaniraptorans perhaps retained this
diet (e.g. _Microraptor_, _Archaeopteryx_).  And although the SLC is often
associated with predatory habits (i.e. lunging at and clutching large prey
with the hands), most SLC-bearing theropods probably weren't hyperpredatory.
Certain taxa lost the SLC altogether - either through degeneration or by
absorption into a coossified structure (e.g. alvarezsaurids, birds).



Tim



------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163