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

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.


Hi everyone!
Any chance for Troodontidae (or some of them) perhaps being omnivors too?
Thanks in advance.

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.