Thescelosaurus

Thescelosaurus is ornithopod dinosaur that appeared in the late Cretaceous period in North America. It’s name means “marvelous lizard”. Thescelosaurus was a bipedal dinosaur that grows to 13 feet and 700 lbs. Thescelosaurs had short, broad, five-fingered hands, and four-toed feet with triangular hoof-like toe claws. It could have been an omnivore based on its skull and its muscular jaw. A Thescelosaurus skeleton named “Willo” found in So. Dakota in 1993 is famous for having a partially preserved heart. There are two species with the most abundant species being Thescelosaurus neglectus.

Thescelosaurus fossils are less abundant than the large theropods and herbiovores in the Hell Creek Fm. A dinosaur census conducted by the Hell Creek Project calculated relative abundance of the Thescelosaurus was 8% of the population. Today, we find fossilized teeth, unguals (claws), spikes, and non-associated bones.

Thescelosaurus tooth identification. Thescelosaurus teeth are routinely identified and sold as Pachycephalosaurus teeth since they maxillary teeth have similar shape and size. There has been some good work done presented in the Fossil Forum. The Fossil Forum author concludes that Pachycephalosaurus maxillary teeth can be differentiated from Thescelosaurus teeth since the Pachy teeth exhibit “vertical ridges are more pounced, fewer and a more prominent center ridge may exist. There is also no symmetry with the crowns.” Several good photographic references are provided. Link to the Fossil Forum discussion. The Thescelosaurus maxillary teeth appear to be very symmetrical with a flat fan like crown and little to no central vertical ridge development in the reference teeth.  That said, rooted teeth from both species are scarce and are highly collectable.

Thescelosaurus ungual (claw) identification. Thescelosaurus unguals (claws) are routinely identified and sold as Pachycephalosaurus unguals as they have a similar shape and size. Unfortunately there is little reference data for Pachycephalosaurus unguals with only one Pachy specimen with partial legs found. Per my discussion with the primary Fossil Forum Hell Creek dinosaurs author, he suggested “to differentiate between the two is Thescelosaurus claws are flat and triangular and the ones with a twist are Pachy”. That said, unguals  (claws) from both species are rare and are highly collectable.