page_title: Thescelosaurus
section_title: Temporal and geographic range
hierarchical_section_title: Thescelosaurus / Paleoecology / Temporal and geographic range
caption_attribution_description: English: Pie chart of the time averaged census for large-bodied dinosaurs from the entire Hell Creek Formation in the study area (sampled near Fort Peck Reservoir in northeastern Montana). Triceratops is the most common dinosaur at 40% (n = 72); Tyrannosaurus is second at 24% (n = 44); Edmontosaurus is third at 20% (n = 36) followed by Thescelosaurus at 8% (n = 15), Ornithomimus at 5% (n = 9), and Pachycephalosaurus and Ankylosaurus at 1% (n = 2).
context_page_description: Thescelosaurus was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous–Paleogene extinction event around 66 million years ago. The preservation and completeness of many of its specimens indicate that it may have preferred to live near streams.
  This bipedal ornithopod is known from several partial skeletons and skulls that indicate it grew to between 2.5 and 4.0 meters in length on average. It had sturdy hind limbs, small wide hands, and a head with an elongate pointed snout. The form of the teeth and jaws suggest a primarily herbivorous animal. This genus of dinosaur is regarded as a specialized basal ornithopod, traditionally described as a hypsilophodont, but more recently recognized as distinct from Hypsilophodon. Several species have been suggested for this genus. Three currently are recognized as valid: the type species T. neglectus, T. garbanii and T. assiniboiensis.
  The genus attracted media attention in 2000, when a specimen unearthed in 1993 in South Dakota, United States, was interpreted as including a fossilized heart.
context_section_description: True Thescelosaurus remains are known definitely only from late Maastrichtian-age rocks, from Alberta (Scollard Formation) and Saskatchewan (Frenchman Formation), Canada, and Wyoming (Lance Formation), South Dakota (Hell Creek Formation), Montana (Hell Creek), and Colorado (Laramie Formation), USA. With the exception of birds, it was one of the last genera of dinosaurs, its remains being found as close as 3 meters to the boundary clay containing the iridium layer that closes the Cretaceous. The Laramie Formation is the oldest formation that Thescleosaurus is known from, and magnetostratigraphy suggests an age of 69-68 Ma for the Laramie Formation. There are reports of teeth from older, Campanian-age rocks, particularly from the Dinosaur Park Formation of Alberta, but these specimens are not from Thescelosaurus and are much more likely those of Orodromeus. More specimens are known than have been officially described for this genus, such as the Triebold specimen, which has been the source of several skeletal casts for museums.
  When Galton revisited Thescelosaurus and Bugenasaura in 1999, he described the dentary tooth UCMP 46911 from the Upper Jurassic of Weymouth, England as cf. Bugenasaura. If it is indeed a tooth from a thescelosaur-like animal, this would significantly extend the stratigraphic range of the group.
caption: Pie chart of the time averaged census for large-bodied dinosaurs from the entire Hell Creek Formation in the study area
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