Falcarius utahensis Therizinosaur skeleton fossil cast
Therizinosaur skull cast replica
This new discovery was described in the May 5th issue of Nature. It is the earliest and most primitive Therizinosauroid to this date, and the fact that it has been found in North America, not in Asia, is a surprise since until now most Therizinosaurs have been found there.
Falcarius utahensis has uniquely primitive features for this group. Its femur was longer than its tibia, which is not the case in more derived therizionsaurs that have the inverse condition. This points to a quicker locomotion and Dr. James Kirkland et al. believe that it shows that the animal had an omnivorus diet, instead of the vegetarian diet proposed for later therizinosaurs. Also the pelvis is only slightly widened, an adaptation necessary to accommodate the longer gut needed to extract nutrients from plants. The tail which is reduced in most therizinosaurs is very long in this species and the hands do not have the extremely long claws seen in Therizinosaurus.
The bonebed believed to contain more than 1 million bones of this animal was discovered by Lawrence Walker, a commercial fossil collector. Realizing the importance of his find he took Dr. Kirkland to the site. Apparently the site contains the bones of babies, juveniles and adults, possibly even males and females.
References Kirkland J. I., Zanno L. E., Sampson S. D., Clark J. M. & Beblieux D. D. (2005). A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. Nature, 434. Pp: 84-87.
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