Genasauria
Genasauria is a clade that encompasses the great majority of ornithischian dinosaurs, excluding only the earliest-diverging forms such as Lesothosaurus. It unites two major branches: Thyreophora, the armored dinosaurs including ankylosaurs, stegosaurs, and more primitive relatives like Scelidosaurus; and Cerapoda, which gathers the ornithopods, ceratopsians, pachycephalosaurs, and various small early forms. Members were primarily herbivores that typically held their heads about a meter off the ground, suggesting they fed mainly on ground-level plants such as ferns, cycads, and other low-growing gymnosperms. A hallmark of the group is the presence of fleshy cheeks bounding inset tooth rows, an adaptation for more efficient processing of plant material in the mouth.
Diagnosis
- Buccal emargination of the tooth rows, with maxillary and dentary teeth inset from the lateral jaw margin (implying muscular cheeks)
- Spout-shaped, edentulous anterior margin of the predentary and premaxilla
- Reduced number of premaxillary teeth
- Cheek-tooth crowns bearing a prominent primary ridge
Clades within Genasauria
- Thyreophora 123 genera
- Neornithischia 347 genera
Genera placed directly in Genasauria
- Peishansaurus Nomen dubium Barremian–Albian (125.8–100.5 Ma)Chinaincertae sedisunder dispute
- Serendipaceratops Disputed Aptian (121.4–113.2 Ma)Australiaincertae sedis
References
-
Sereno, P. C. (1986). Phylogeny of the bird-hipped dinosaurs (Order Ornithischia). National Geographic Research 2(2): 234-256.
Erected Genasauria.
sereno1986a -
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
Provides the modern phylogenetic definition of Genasauria.
madzia2021a