Open Paleo

Thescelosauridae

Sternberg, 1937 Type genus Thescelosaurus

Its genera lived 121.4–66.0 million years ago Early Cretaceous–Late Cretaceous
Early Cretaceous and Late Cretaceous stages

Thescelosauridae is a clade of small to medium-sized neornithischian dinosaurs from the Cretaceous of North America, East Asia and South America, lying outside the more derived Cerapoda. It is divided into two subgroups (Madzia and colleagues, 2021): Orodrominae, which includes Orodromeus, Oryctodromeus, Zephyrosaurus and Albertadromeus along with the Asian Changchunsaurus, Haya and Koreanosaurus, and Thescelosaurinae, which unites Parksosaurus, Thescelosaurus and the South American Notohypsilophodon. Other analyses instead place Jeholosaurus, Changchunsaurus and other small Asian forms within Thescelosaurinae (Fonseca and colleagues, 2024; Jung and colleagues, 2026). Its members were stocky, ground-dwelling herbivores that browsed selectively on soft, pulpy plant matter. Some of the orodromines appear to have been burrowers, a habit demonstrated by Oryctodromeus, whose remains have been found preserved within a burrow. The name Parksosauridae has been applied to the same group, but Thescelosauridae is the older name.

Diagnosis

  1. Fossa developed on the premaxilla-maxilla boundary
  2. Fossa on the pterygoid wing of the quadrate
  3. Laterally flattened greater trochanter of the femur
  4. Overhanging lateral condyle of the tibia
  5. Squared to rounded lateral distal tarsal

Clades within Thescelosauridae

Genera placed directly in Thescelosauridae

  • Nevadadromeus Bonde et al., 2022 Cenomanian (100.5–93.9 Ma)United Statesincertae sedisunder dispute

References

  1. Sternberg, C. M. (1937). Classification of Thescelosaurus, with a description of a new species. Proceedings of the Geological Society of America 1936: 375.

    Origin of the family-group name Thescelosauridae.

    sternberg1937a
  2. Madzia, D.; Arbour, V. M.; Boyd, C. A.; Farke, A. A.; Cruzado-Caballero, P.; Evans, D. C. (2021). The phylogenetic nomenclature of ornithischian dinosaurs. PeerJ 9: e12362. doi:10.7717/peerj.12362

    Defined Thescelosauridae and listed Parksosauridae Buchholz, 2002 as a name used for the same contents.

    madzia2021a
  3. Buchholz, P. W. (2002). Phylogeny and biogeography of basal Ornithischia. The Mesozoic in Wyoming, Tate 2002 18-34. Tate Geological Museum.

    Coined Parksosauridae, a junior synonym covering the same clade as Thescelosauridae.

    buchholz2002a
  4. Fonseca, A. O.; Reid, I. J.; Venner, A.; Duncan, R. J.; Garcia, M. S.; Müller, R. T. (2024). A comprehensive phylogenetic analysis on early ornithischian evolution. Journal of Systematic Palaeontology 22: 2346577. doi:10.1080/14772019.2024.2346577

    Recovered Jeholosaurus and Changchunsaurus within Thescelosaurinae, rendering Jeholosauridae inapplicable.

    fonseca2024a
  5. Jung, J.; Kim, M.; Jo, H.; Clarke, J. A. (2026). A new dinosaur species from Korea and its implications for early-diverging neornithischian diversity. Fossil Record 29(1): 87-113. Pensoft Publishers. doi:10.3897/fr.29.178152

    Described Doolysaurus and recovered it and other small Asian taxa within Thescelosaurinae in the Fonseca dataset.

    jung2026a