Re: Falcarius utahensis (was RE: Newfound Dinosaur a Transitional Creature)

[Amtoine Grant <ajgrant@eastlink.ca>]

On Wednesday, May 4, 2005, at 04:57  PM, TooTs wrote:

> > Therizinosauroidea] had already undertaken the initial steps in this
> > But I wonder if this transition might have begun even earlier,
> > based on the dentition of troodontids and the posterior shift of the 
> > pubic
> > shaft that appears to be primitive for the Maniraptora.
> >
> >
> >
> > Tim
> Hi everyone!
> Any chance for Troodontidae (or some of them) perhaps being omnivors 
> too?
> Thanks in advance.
> TooTs

I thought that that was the prevailing theory for troodontids. In my 
armchair-palaeontological studies I've come to the following 
conclusion. Ornithomimids and therizinosaurids are sister groups. 
Referring to my 2D skeletal drawings by Greg Paul, the hips do support 
this. Derived therizinosaurids have an exaggerated anterior process of 
the ilium that extends downward. Falcarius shows a less-extensive step 
in this trend. Gallimimus, among other ornithomimids, shows a slightly 
less dramatic version of this as well. The main differences that I can 
see make sense given the future of the linneages, such as elongation of 
the forearm claws to be used as defense instead of their running 
ability. The "boot"-ending of Falcarius is lost in later 
therizinosaurids, but present in, and strongly similiar to, 
ornithomimids.
I propose that troodontids branched off from the common 
troodontid/ornithomimid/therizinosaurid ancestor earlier in the 
transition to herbivory than the rest, partially explaining their tooth 
morphology and more obvious retainment of a prdatory body plan. The 
ischium of Falcarius is very troodontid-like above anything else 
besides an oviraptorid's. Therizinosaurids appear to have assumed a 
sloth-like status of being more stationary and evolved their long 
bladelike claws for defense(see Chased by Dinosaurs - Giant Claw). 
Ornithomimids, on the other hand, appear to have instead simply 
continued and even got better at high-speed retreat from predators, 
with the option to kick a would-be, rather like ostriches.