Open Paleo

Parksosaurus

Sternberg, 1937 PAHRK-so-SAWR-us

Named after Canadian paleontologist William A. Parks, who discovered the specimen, combined with Greek sauros meaning 'lizard'; meaning 'Parks's lizard'

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Parksosaurus is a genus of neornithischian dinosaur from the early Maastrichtian-aged (Upper Cretaceous) Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur. It is one of the few described non-hadrosaurid ornithopods from the end of the Cretaceous in North America, existing around 70 million years ago.

Under dispute

Parksosaurus is most often recovered within Thescelosaurinae, close to Thescelosaurus (Boyd, 2015; Manitkoon and colleagues, 2023), the position followed by Jones (2026). Herne and colleagues (2019) instead recovered it as the basalmost ornithopod, and Rozadilla and colleagues (2016) near basal Iguanodontia.

Diagnosis

  1. Antorbital fenestra very small, bounded by the maxilla and lacrimal
  2. Posterodorsal end of the jugal expanded anteroposteriorly
  3. Posterior process of the premaxilla deep, allowing extensive maxilla-nasal contact
  4. Cheek teeth with numerous low, rounded, parallel vertical ridges on the thickly enameled crown (labial on maxillary teeth, lingual on dentary teeth)
  5. Frontals narrow and elongate, maximum width about two-thirds of their length
  6. About 18 maxillary and 20 dentary tooth positions per side

Species

Parksosaurus warreni (Parks, 1926)

Type species

First named as Thescelosaurus warreni

Named for Mrs. H. D. Warren, who financially supported the research that led to the description of the holotype specimen.

Holotype
ROM 804 , Royal Ontario Museum
Material
A partial skull with a largely articulated postcranial skeleton (dorsal, sacral and caudal vertebrae, girdles, fore- and hindlimbs) and extensive ossified caudal tendons; cervicals and manus absent.
Horizon
Tolman Member, Horseshoe Canyon Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
half a mile from the Red Deer River, on the east side, immediately south of the road to Rumsey ferry, Alberta, Canada

References

  1. Larson, D. W.; Brinkman, D. B.; Bell, P. R. (2010). Faunal assemblages from the upper Horseshoe Canyon Formation, an early Maastrichtian cool-climate assemblage from Alberta, with special reference to the Albertosaurus sarcophagus bonebed. Canadian Journal of Earth Sciences 47(9).

    Places the type in unit 4 of the upper Horseshoe Canyon Formation.

    larson2010a
  2. Eberth, D. A.; Braman, D. R. (2012). A revised stratigraphy and depositional history for the Horseshoe Canyon Formation (Upper Cretaceous), southern Alberta plains. Canadian Journal of Earth Sciences 49(9): 1053-1086. Canadian Science Publishing. doi:10.1139/e2012-035

    Defines the Tolman Member as the combined units 3 and 4 of the Horseshoe Canyon Formation.

    eberth2012a
  3. Parks, W. A. (1926). Thescelosaurus warreni, a new species of orthopodous dinosaur from the Edmonton Formation of Alberta. University of Toronto Studies (Geological Series) 21: 1-42.

    Original description of the holotype (ROM 804) as Thescelosaurus warreni; source of the holotype material. Sternberg (1937) later made it the type of Parksosaurus.

    parks1926b
  4. Sternberg, C. M. (1937). Classification of Thescelosaurus, with a description of a new species. Proceedings of the Geological Society of America 1936: 375. sternberg1937a
  5. Galton, P. M. (1973). Redescription of the skull and mandible of Parksosaurus from the Late Cretaceous with comments on the family Hypsilophodontidae (Ornithischia). Life Sciences Contribution, Royal Ontario Museum 89: 1-21.

    Modern redescription of the skull and mandible; source of the diagnostic features.

    galton1973b
  6. Manitkoon, S.; Deesri, U.; Khalloufi, B.; Nonsrirach, T.; Suteethorn, V.; Chanthasit, P.; Boonla, W.; Buffetaut, E. (2023). A New Basal Neornithischian Dinosaur from the Phu Kradung Formation (Upper Jurassic) of Northeastern Thailand. Diversity 15(7). MDPI AG. doi:10.3390/d15070851

    Recovered Parksosaurus within Thescelosaurinae close to Thescelosaurus.

    manitkoon2023a
  7. Herne, M. C.; Nair, J. P.; Evans, A. R.; Tait, A. M. (2019). New small-bodied ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic rift system, with revision of Qantassaurus intrepidus Rich and Vickers-Rich, 1999. Journal of Paleontology 93(3): 543-584. Cambridge University Press (CUP). doi:10.1017/jpa.2018.95

    Recovered Parksosaurus as the basalmost ornithopod.

    herne2019a
  8. Rozadilla, S.; Agnolín, F. L.; Novas, F. E.; Aranciaga Rolando, A. M.; Motta, M. J.; Lirio, J. M.; Isasi, M. P. (2016). A new ornithopod (Dinosauria, Ornithischia) from the Upper Cretaceous of Antarctica and its palaeobiogeographical implications. Cretaceous Research 57: 311-324. Elsevier BV. doi:10.1016/j.cretres.2015.09.009

    Recovered Parksosaurus near basal Iguanodontia.

    rozadilla2016a
  9. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Treats Parksosaurus as a thescelosaurine.

    jones2026a
  10. Boyd, C. A. (2015). The systematic relationships and biogeographic history of ornithischian dinosaurs. PeerJ 3: e1523. PeerJ. doi:10.7717/peerj.1523

    Recovered Parksosaurus within Thescelosaurinae, close to Thescelosaurus.

    boyd2015a