Thescelosaurus was a small plant-eating dinosaur which was among the last of its kind and was probably wiped out in the final extinction 65 million years ago. It was also one of those "basement discoveries," dug up in 1891 and stored away for more than 20 years before it was re-discovered in its packing crate.
In 1993 a very fine specimen was discovered in South Dakota by amateur paleontologist Mike Hammer. This skeleton had a complete skull that showed a very efficient set of at least three different types of teeth, and contained evidence that this dinosaur had cheeks that would have improved its food processing efficiency. Bipedal, with a relatively long tail, its front legs were sturdy, but not particularly long. It had fairly long front claws, which may have been useful for digging. Its hind legs were not built for the speed evidenced by other members of the hypsilophodont family.
One of the most unusual aspects of the 1993 specimen is that it seems to have a fossilized heart. This was widely publicized, and following studies conducted by Dr. Dale Russell, it was concluded that the heart's structure suggests an intermediate form somewhere between crocodiles and birds. Many scientists feel that this is evidence that some dinosaurs had high metabolic rates, suggesting that they were warm-blooded. One of the most spectacular fossil finds of all time, the specimen is on display at the North Carolina Museum of Natural Sciences.
It is mentioned in an educational book on Tyrannosaurus rex.