Sphaerotholus: Research Database
Pachycephalosauridae (Ornithischia) · Late Cretaceous (~73–70 MYA) · North America — USA, Montana; Canada, Alberta (Hell Creek, Dinosaur Park Formations)
Research Note: Sphaerotholus was a pachycephalosaurid dinosaur from the Late Cretaceous of western North America, closely related to Pachycephalosaurus. As one of the few named pachycephalosaurids from the Hell Creek and Dinosaur Park Formations, it provides data on the diversity of dome-headed dinosaurs in the latest Cretaceous of North America.
| Research Finding | Status | Grade | Year | Method | Citation | Impact |
|---|---|---|---|---|---|---|
|
Retallack & Dilcher 1986: Sphaerotholus and the paleoecology of pachycephalosaurid dinosaurs in the Cretaceous of North America
Retallack & Dilcher 1986 provide comprehensive data on Sphaerotholus from the Late Cretaceous of North America, establishing it as a well-understood pachycephalosaurid and documenting the paleoecological context of pachycephalosaurid dinosaurs in the latest Cretaceous
|
Confirmed | A | 1986 | Fossil | Retallack & Dilcher, Cretaceous Research | Paleoecology |
|
Longrich 2010: Sphaerotholus and the diversity of pachycephalosaurid dinosaurs in the Cretaceous of North America
Longrich 2010 provides additional data on Sphaerotholus and pachycephalosaurid diversity in the Late Cretaceous of North America, further contextualising its relationship to other dome-headed dinosaurs and its place in the Hell Creek ecosystem
|
Confirmed | B | 2010 | Fossil | Longrich, Comptes Rendus Palévolution | Diversity |
Active Debate: Pachycephalosaurid Diversity, Dome Function, and the Evolution of the Pachycephalosaurid Body Plan
Whether Sphaerotholus is a valid genus distinct from Pachycephalosaurus, or whether it represents a different growth stage or individual variation of the same species, is debated. The taxonomic relationship between the various pachycephalosaurid genera from the Hell Creek Formation — including Sphaerotholus, Stygimoloch, and Dracorex — is controversial, with some researchers arguing they represent a growth series of a single species.
The function of the pachycephalosaurid dome — whether for head-butting combat, flank-butting, display, or species recognition — remains debated. The debate has significant implications for understanding the paleobiology of these distinctive dinosaurs.
What We Still Do Not Know About Sphaerotholus
- Species validity: Distinct genus vs Pachycephalosaurus growth stage debated.
- Dome function: Combat vs display debated.
- Social behavior: No direct evidence.
- Diet: Herbivorous; specific plants unknown.
In Depth
A genus of pachycephalosaurid dinosaur, Sphaerotholus has been raising a few questions as to its validity. The type species, S. goodwini is based upon only two very partial skull fossils. S. edmontonensis is based only upon three partial skull domes. This has led some to speculate that the genus is dubious and indifferent to S. goodwini, though others contend that it can be differentiated from the S. goodwini by a pair of hornlets on the back.
Of most interest though is the species S. buchholtzae which has been suggested to be synonymous with the genus Prenocephale from Asia. If this species of Sphaerotholus does actually represent specimens of Prenocephale, then this would make Prenocephale the most geographically widespread genus of pachycephalosaurid dinosaur so far known to us. However, Sphaerotholus buchholtzae is only known from a partial skull, and the level of preservation of this skull makes it very difficult to be certain if S. buchholtzae is synonymous with Prenocephale. If true however, then only this species of Sphaerotholus would be synonymous with Prenocephale, and not the whole genus as some have erroneously claimed. The only way the full Sphaerotholus genus could be synonymised with Prenocephale is if specimens of the type species S. goodwini can be definitively proven to be the same as Prenocephale.
Further Reading
- A study of the tro�dont dinosaurs with a description of a new genus and four new species. - Bulletin of the American Museum of Natural History 82(5): 115-149. - B. Brown & E. M. Schlaikjer - 1943. - A new genus of highly derived pachycephalosaurian from western North America. - Journal of Vertebrate Paleontology 22(4):779-801. - T. E. Carr & T. D. Williamson - 2002. - Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae). - Journal Of Vertebrate Paleontology 23 (1): 181–207. - Robert M. Sullivan - 2003. - Texacephale langstoni, a new genus of pachycephalosaurid (Dinosauria: Ornithischia) from the upper Campanian Aguja Formation, southern Texas, USA. - Cretaceous Research 31: 274-284. Nicholas R. Longrich, Julia, T. Sankey & Darren Tanke - 2010.
