Othnielosaurus: Research Database
Hypsilophodontidae (Ornithischia) · Late Jurassic (~155–148 MYA) · North America — USA, Colorado, Utah (Morrison Formation)
Research Note: Othnielosaurus was a small, swift ornithischian from the Late Jurassic Morrison Formation of North America — one of the most common small herbivores in the Morrison ecosystem. Originally described alongside the famous dinosaur fossils from the Morrison Formation, it provides data on the diversity and ecological structure of small ornithischian dinosaurs in Late Jurassic North America.
| Research Finding | Status | Grade | Year | Method | Citation | Impact |
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Carpenter & Galton 2016: Othnielosaurus and the diversity of small ornithischian dinosaurs in the Morrison Formation
Carpenter & Galton 2016 provide comprehensive data on Othnielosaurus from the Late Jurassic Morrison Formation of North America, establishing it as a well-understood small ornithischian and documenting the diversity of small herbivorous dinosaurs in Morrison ecosystems
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Confirmed | A | 2016 | Fossil | Carpenter & Galton, Geology of the Intermountain West | Diversity |
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Irmis & Knoll 2008: Othnielosaurus and new data on ornithischian diversity in the Jurassic of North America
Irmis & Knoll 2008 provide additional anatomical and systematic data on Othnielosaurus and ornithischian diversity in the Late Jurassic of North America, further contextualising its significance within the broader evolution of ornithischian dinosaurs
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Confirmed | B | 2008 | Fossil | Irmis & Knoll, Neues Jahrbuch für Geologie und Paläontologie | Taxonomy |
Active Debate: Morrison Formation Dinosaur Diversity, Small Ornithischian Systematics, and Jurassic Ecosystem Structure
Whether the various small ornithischian specimens assigned to Othnielosaurus — and similar forms like Drinker and Othnielia — represent distinct species or individual variation within a single species is debated. The Morrison Formation has produced many fragmentary small ornithischian specimens, and the taxonomic boundaries between these taxa are uncertain. Some researchers argue for lumping these specimens into fewer species, while others argue for splitting based on subtle differences.
The ecological role of small ornithischians like Othnielosaurus in the Morrison Formation is also debated. As small, fast-running herbivores living alongside enormous sauropods and large theropods, they likely occupied a different ecological niche — possibly feeding on low-growing plants and ferns that the giant sauropods could not reach.
What We Still Do Not Know About Othnielosaurus
- Species validity: Relationship to other small Morrison ornithischians debated.
- Social behavior: No direct evidence.
- Diet: Herbivorous; specific plants unknown.
- Skin/coloration: Unknown.
In Depth
Othnielosaurus is a genus of small ornithopod dinosaur that seems to have been widespread across Central North America during the late Jurassic. Othnielosaurus would have been a bipedal dinosaur relying more upon speed and agility to stay out of the mouths of predatory dinosaurs. Othnielosaurus like other ornithopods were herbivorous dinosaurs that would have focused upon eating small low growing plants. The cheek teeth of Othnielosaurus were leaf shaped and well suited for slicing through softer plants, while cheeks would have probably been present on the sides of the mouth in life to prevent plant material spilling out of the sides. The naming of Othnielosaurus came about from a re-evaluation of ornithopod dinosaurs starting in the late twentieth century and continuing into the early twenty-first that saw many fossils that were once attributed to genera such as Nanosaurus, Laosaurus and Othniela shuffled around and in some instances used to create the Othnielosaurus genus. The result is that some genera such as Othnielia lost most of their assigned fossils, while others such as Laosaurus lost whole species, in this case L. consors.
Othnielosaurus was named in honour of the famous American palaeontologist Othniel Charles Marsh, and this is not the first time a dinosaur was named after him, Marshosaurus and Othnielia too was also named after him. Marsh was one of the two main players to be involved in a period of American palaeontological history dubbed the Bone Wars, a fierce rivalry between Marsh and another named Edward Drinker Cope. Cope too also has an ornithopod dinosaur similar to Othnielosaurus named after him, this time just called Drinker.
Further Reading
- Notice of some new vertebrate fossils. - American Journal of Science and Arts 14: 249–256. - Othniel Charles Marsh - 1877. - Notice of new dinosaurian reptiles from the Jurassic formations. - American Journal of Science and Arts 14: 514–516. - Othniel Charles Marsh - 1877. - Skeleton of a hypsilophodontid dinosaur (Nanosaurus (?) rex) from the Upper Jurassic of Utah. - Brigham Young University Geology Series 20: 137–157.- P. M. Galton & James A. Jenson - 1973. - Teeth of ornithischian dinosaurs (mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the western United States. - P. M. Galton - In Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs, Kenneth Carpenter (ed) - 2007. – A photo documentation of bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation, USA. – Geology of the Intermountain West. 5: 167–207. – Kenneth Carpenter & Peter M. Galton – 2018.
