Ankylopollexia

synapomorphic feature of a conical thumb spine defines the clade.^[2]

herbivorous.^[3]

hadrosaurs. There are, however, exceptions to this trend. A single track from a large ornithopod, likely a relative of Camptosaurus, was reported from the Lourinhã Formation, dating to the Jurassic in Portugal. The corresponding animal had an estimated hip height of around 2.8 metres (9.2 ft), much larger than the contemporary relative Draconyx.^[7] The primitive styracosternan Iguanacolossus was named for its distinct robustness and large size, likely around 9 metres (30 ft) in length.^{[citation needed]} Regarding hadrosaurs, one of the more basal members of Hadrosauroidea, the Chinese genus Bolong, is estimated to have been around 200 kilograms (440 lb).^[8] Another exception of this trend is Tethyshadros, a more derived genus of Hadrosauroidea. Estimated to have weighed 350 kilograms (770 lb), Tethyshadros have been found only on certain islands in Italy. Its diminutive size is explained by insular dwarfism.^[9] In addition a 44 cm scapula belonging to an ankylopollexian has been found in the lourinha formation^[10]

phylogenetic definition was given: the last common ancestor of the species Camptosaurus dispar and Parasaurolophus walkeri and all its descendants.^{[citation needed}

Claosaurus annectens (today referred to the genus Edmontosaurus^[16]) was used by Othniel Charles Marsh to create a cast of the brain cavity. Some basics remarks were made, including the small size of the organ, but interpreting minute features of the organ was noted to be difficult.^[17] The 1897 paper noted the similarity of the two endocasts.^[15]

ornithischian dinosaurs as a whole. The brains of a large variety of taxa have been studied. John Ostrom, would, in 1961, provide what was then the most extensive and detailed review and work on hadrosaur neuro-anatomy. This area of hadrosaur study was in its infancy at this point, and only the species known today as Edmontosaurus annectens, Edmontosaurus regalis, and Gryposaurus notabilis (at that time thought to be a synonym of its relative Kritosaurus) had specimens suitable at the time to be examined (Lambeosaurus was listed as having a briefly described braincase, but this was a mistake originating in Lull and Wright (1942)).^[18][19] Ostrom supported the view that the brains of hadrosaurs and other dinosaurs would've likely only filled a portion of the cranial cavity, therefore hindering the ability to learn from endocasts, but noted they were still useful. He noted, similar to Marsh, noted the small predicted size of the organ, but also that it was significantly developed. A number of similarities to the brains of modern reptiles were noted.^[19]

intraspecific behaviours as indicated by their acoustic and visual display structures.^[20]

neural tissues seemed to be very tightly packed, indicating an EC closer to five (with hadrosaurs having even higher ECs), nearly matching that of the most intelligent non-avian theropods. Though it was noted this was in-line with their complex behaviour, as had been noted by Hopson, it was cautioned the dense packing may have been an artifact of preservation, and the original lower estimates were considered more accurate. Some of the complex behaviours ascribed can be seen to some extent in modern crocodilians, who fall near the original numbers.^[13]

sauropods and other ornithischians, but different EQ estimates for theropods were cited, placing the hadrosaur numbers significantly below the majority of theropods. Additionally, the relative cerebral volume was only 30% in Amurosaurus, significantly lower than in Hypacrosaurus, closer to that of theropods like Tyrannosaurus, though still distinctly larger than previously estimated numbers for more primitive iguanodonts. This demonstrated a previously unrecognized level of variation in neuro-anatomy within Hadrosauridae.^[21]

Camptosaurus dispar, which dates to around the Callovian-Oxfordian, about 156-157 million years ago.^[24]