THE CRANIAL ENDOCAST OF LATE CRETACEOUS HADROSAUR MAIASAURA PEEBLESORUM AND ITS IMPLICATIONS FOR SENSORY FUNCTIONS

Hadrosaurids exhibited extreme morphological diversity and behavioral characteristics that can be compared with other, closely related members of Dinosauria – particularly through the study of neuroanatomy. The Late Cretaceous saurolophine hadrosaur Maiasaura peeblesorum offers a unique opportunity to compare complex ecological behavior alongside X-ray CT generated endocranial data between other non-avian dinosaurs and their modern archosaur relatives. By observing measurements and calculations taken from the cranial endocast and endosseous labyrinths of an adult M. peeblsorum, the olfactory acuity, various encephalization quotients, and average and best hearing frequencies can be deduced. Relevant data from the endocranial anatomy of M. peeblesorum indicates that adults of the species would have had an average to high olfactory acuity, cerebral telencephalon-to-total endocranial volume of 49.5%, a high reptile encephalization quotient, and average and best hearing frequency of 2050 Hz and 3380 Hz respectively. The cerebral telencephalon volume is 6% higher than other calculated volumes of other hadrosaurs, suggesting enhanced cognitive abilities, which is consistent with the advanced social and nesting behavior seen in the fossilized record associated with this species. The neuroanatomy and other calculated traits of M. peeblesorum are similarly consistent in comparison with other ornithopod taxa, such as Gryposaurus, Hypacrosaurus, and Iguanodon, which are to be expected given their close relationship to each other. M. peeblesorum is an exemplar taxon that preserves numerous growth stages and complex behavior related to parental care and socialization. Therefore, these preliminary neuroanatomical descriptions and sensory calculations for a Maiasaura adult are critical in understanding how sensory acuity and behavior may have changed ontogenetically and interspecifically.