Hadrosauromorpha
Hadrosauromorpha is a clade of iguanodontian ornithopods that divides the broader hadrosauroids into the basal forms, which retain compressed hand bones and a spike-like thumb, and the more derived forms that have lost them. It comprises the duck-billed hadrosaurids together with the stem taxa immediately ancestral to them, a group that has variously been taken to include Tethyshadros, Bactrosaurus, Gilmoreosaurus, Telmatosaurus, and Levnesovia, though membership shifts from one analysis to another and their internal relationships remain poorly resolved. Members are distinguished by a suite of skull and skeletal traits approaching the hadrosaurid condition: the loss of the thumb spike and reduced, less mobile wrist and hand, more slender lower forelimb bones, shoulder blades bearing an overhanging projection rather than a J-shaped curve, a straight thigh bone, and shortened foot bones. These animals lived across Eurasia and North America during the Cretaceous, forming the evolutionary grade leading up to the true duck-billed dinosaurs.
Diagnosis
- Loss of the surangular foramen
- Shallow embayment of the jugal wing of the quadrate
- Reduction of the antorbital fenestra
- Further elaboration of the dental battery toward the hadrosaurid condition
Clades within Hadrosauromorpha
- Hadrosauridae 72 genera
Genera placed directly in Hadrosauromorpha
- Bactrosaurus Coniacian–Maastrichtian (89.8–66.0 Ma)China
- Claosaurus Coniacian–Campanian (89.8–72.2 Ma)United Statesunder dispute
- Eolambia Cenomanian (100.5–93.9 Ma)United Statesunder dispute
- Fylax Maastrichtian (72.2–66.0 Ma)Spain
- Gilmoreosaurus Coniacian–Maastrichtian (89.8–66.0 Ma)China
- Gobihadros Cenomanian–Santonian (100.5–83.6 Ma)Mongolia
- Gonkoken Maastrichtian (72.2–66.0 Ma)Chile
- Huehuecanauhtlus Santonian (85.7–83.6 Ma)Mexico
- Jeyawati Turonian (93.9–89.8 Ma)United States
- Jintasaurus Aptian (121.4–113.2 Ma)Chinaunder dispute
- Kryptohadros Maastrichtian (72.2–66.0 Ma)Romaniaunder dispute
- Levnesovia Turonian (93.9–89.8 Ma)Uzbekistan
- Lophorhothon Santonian–Campanian (85.7–72.2 Ma)United Statesunder dispute
- Nanningosaurus Cenomanian–Maastrichtian (100.5–66.0 Ma)China
- Nanyangosaurus Turonian–Campanian (93.9–72.2 Ma)China
- Plesiohadros Campanian (83.6–72.2 Ma)Mongolia
- Protohadros Cenomanian (100.5–93.9 Ma)United Statesunder dispute
- Shuangmiaosaurus Albian–Cenomanian (113.2–93.9 Ma)China
- Tanius Campanian–Maastrichtian (83.6–66.0 Ma)China
- Telmatosaurus Maastrichtian (72.2–66.0 Ma)Romaniaunder dispute
- Tethyshadros Campanian (83.6–72.2 Ma)Italyunder dispute
- Zhanghenglong Santonian (85.7–83.6 Ma)China
References
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Norman, D. B. (2014). Iguanodonts from the Wealden of England: do they contribute to the discussion concerning hadrosaur origins?. Hadrosaurs 10-43. Indiana University Press, Bloomington.
Named Hadrosauromorpha as a new clade: Parasaurolophus walkeri and all taxa closer to it than to Probactrosaurus gobiensis.
norman2014b -
Norman, D. B. (2015). On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna). Zoological Journal of the Linnean Society 173: 92-189. doi:10.1111/zoj.12193
Ranked Hadrosauromorpha as a cohort and redefined it on Edmontosaurus regalis rather than Parasaurolophus walkeri.
norman2015a -
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 Hadrosauromorpha.
madzia2021a