Appendicular skeleton ofProtoceratops andrewsi(Dinosauria, Ornithischia): comparative morphology, ontogenetic changes, and the implications for non-ceratopsid ceratopsian locomotion

Abstract

Protoceratops andrewsi is a well-known ceratopsian dinosaur from the Djadokhta Formation (Upper Cretaceous, Mongolia). Since the 1920s, numerous skeletons of different ontogenetic stages from hatchlings to adults, including fully articulated specimens, have been discovered, but the postcranial anatomy of Protoceratops has not been studied in detail. A new, mostly articulated subadult individual provides an excellent opportunity for us to comprehensively describe the anatomy of the limb skeleton, to compare to other ceratopsian dinosaurs, and to study the ontogenetic and intraspecific variation in this species. New data provided by the specimen shed light on the lifestyle of P. andrewsi. The young subadult individuals present an array of morphological characters intermediate between the bipedal Psittacosaurus and fully quadrupedal adult P. andrewsi. We compare these observations with a broad range of non-ceratopsid Neoceratopsia (of various locomotor adaptations) and Psittacosauridae (obligate bipeds), which gives us insight into the evolution of the skeletal characters informative for the postural change in ceratopsian dinosaurs.

Relationships of mass properties and body proportions to locomotor habit in terrestrial Archosauria

“…While the same computational models were used in the present study and that of Otero et al (2019), they were analyzed and interpreted differently (one mechanistically, the other statistically), such that the consilience of interpretations further supports a shift in locomotor mode as Mussaurus matured. Ontogenetic changes in locomotor mode have been proposed for other extinct terrestrial archosaurs (e.g., Heinrich et al 1993;Dilkes 2001;Zhao et al 2013;Słowiak et al 2019;Chapelle et al 2020), and it would be interesting to explore the applicability of the current study's approach to testing these interpretations in the future.…”

Pedal proportions of small and large hadrosaurs and other potentially bipedal ornithischian dinosaurs

“…These include some basal ceratopsians (cf. Chinnery and Horner 2007;Senter 2007;Lee et al 2011;Morschhauser et al 2018;Slowiak et al 2019). We did not, however, include stegosaurs, which some authors (e.g.…”

Dinosaur senescence: a hadrosauroid with age-related diseases brings a new perspective of “old” dinosaurs

“…The latter three were used interchangeably referring to exceptionally large individuals, but their definitions are ambiguous. In non-avian dinosaurs these classes were usually suggested based on large size 6 ; nearly all cranial sutures ossified 7 ; fusion of axial elements 6 , 8 ; ossification of the postcranial bones 6 ; presence of the EFS 9 – 11 ; presence of the outer circumferential layer 12 ; and/or multiple generations of secondary osteons 13 . Given natural size variability, large size alone does not necessarily indicate advanced ontogenetic age, without combination with other features 2 .…”