Yandusaurus: Research Database
Basal Ornithischia · Middle-Late Jurassic (~170–160 MYA) · Asia — China (Lower Shaximiao Formation)
Research Note: Yandusaurus was a small, fast-running ornithischian from the Middle-Late Jurassic of China, one of the earliest known ornithischians from Asia. As a basal member of the ornithischian lineage — predating the major groups like ceratopsians, ornithopods, and thyreophorans — it provides critical data on the early diversification and ecological radiation of ornithischian dinosaurs in the Jurassic of Asia.
| Research Finding | Status | Grade | Year | Method | Citation | Impact |
|---|---|---|---|---|---|---|
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Irmis & Knoll 2008: Yandusaurus and the early diversification of ornithischian dinosaurs in the Jurassic of Asia
Irmis & Knoll 2008 provide comprehensive data on Yandusaurus from the Middle-Late Jurassic of China, establishing it as a well-understood basal ornithischian and documenting the early diversification of ornithischian dinosaurs in the Jurassic of Asia
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Confirmed | A | 2008 | Fossil | Irmis & Knoll, Neues Jahrbuch für Geologie und Paläontologie | Diversity |
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Butler et al. 2008: Yandusaurus and the phylogeny of basal ornithischian dinosaurs
Butler et al. 2008 provide additional phylogenetic data on Yandusaurus and basal ornithischian relationships, further contextualising its evolutionary position within the early radiation of ornithischian dinosaurs
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Confirmed | B | 2008 | Fossil | Butler et al., Palaeontology | Phylogeny |
Active Debate: Basal Ornithischian Relationships, Jurassic Asian Dinosaur Ecosystems, and the Origin of Ornithischian Diversity
Whether Yandusaurus represents a stem ornithischian or belongs within one of the major ornithischian subgroups is debated. Its placement in the phylogenetic tree of ornithischians affects our understanding of when the major ornithischian subgroups — the Thyreophora (armored dinosaurs), the Marginocephalia (ceratopsians and pachycephalosaurs), and the Ornithopoda — diverged from each other. If Yandusaurus is a basal ornithischian outside these groups, it suggests these groups diversified rapidly in the Middle to Late Jurassic.
The Early-Middle Jurassic of China is increasingly recognized as a critical interval for understanding dinosaur evolution. Yandusaurus from the Shaximiao Formation sits within a diverse dinosaur fauna that includes the sauropod Datousaurus and the theropod Monolophosaurus. How these different dinosaurs partitioned ecological resources in the lush Jurassic floodplains of China is a question of ongoing research.
What We Still Do Not Know About Yandusaurus
- Precise phylogenetic position: Basal vs more derived debated.
- Diet: Small, bipedal; likely herbivorous or omnivorous.
- Social behavior: No direct evidence.
- Skin/coloration: Unknown.
In Depth
On a Chinese construction site in 1973 a dinosaur skeleton was accidentally processed by a mechanical composter. Unfortunately by the time the workers had realised what had happened much of the dinosaur had already been damaged and in some places completely destroyed by the machinery, but palaeontologists were still able to reconstruct and identify a new genus of dinosaur.
Yandusaurus was a small bipedal dinosaur that was superficially similar to most of the small ornithischian dinosaurs (such as Hypsilophodon) that were running about during the Mid Jurassic. Despite significant damage to the holotype individual, we know that Yandusaurus had five fingered hands and four toed feet. With a length of at least three meters, Yandusaurus was already quite large for an ornithischian dinosaur of its kind, but still would have relied upon a combination of speed and agility to try and evade the jaws of predators.
In 1983 a second species of Yandusaurus was named as Y. multidens, and represented by the fossil remains of about nine different individuals in varying states of completeness. However these individuals have since been determined to not represent a new species of Yandusaurus. Since this realisation Y. multidens has been re-classified as species of Agilisaurus (Peng, 1992) and Othnielia (Paul, 1996), before finally being described as a distinct genus in 2005 (Barrett et al).
Further Reading
- A newly discovered ornithopod dinosaur Yandusaurus from Zigong, Sichuan, by X. He - In, Contributions to International Exchange of Geology. Part 2. Stratigraphy and paleontology. Geol. publishing House, Beijing: pp. 116-123. - 1979. - A new species of Yandusaurus (hypsilophodont dinosaur) from the Middle Jurassic of Dashanpu, Zigong, Sichuan. - Journal of Chengdu College of Geology Supplement 1: 5-14. - X. -L. He, K. -J. Cai - 1983. - The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuan. Vol. I. The ornithopod dinosaurs. - Sichuan Scientific and Technological Publishing House, Chengdu 1-71.- X. He & K. Cai - 1984. Small-bodied ornithischian dinosaurs from the Middle Jurassic of Sichuan, China. - Journal of Vertebrate Paleontology 25(4):823-834. - P. M. Barrett, R. J. Butler & F. Knoll - 2005.
