Hands, feet, and behaviour in Pinacosaurus (Dinosauria: Ankylosauridae)

Structure of the manus and pes has long been a source of confusion in ankylosaurs, owing to the imperfect preservation or complete lack of these parts of the skeletons in most specimens, and the fact that many species appear to have undergone a reduction in numbers of digits and phalanges. New specimens of Pinacosaurusfrom Alag Teeg in Mongolia confirm that the phalangeal formula of the manus is 2−3−3−3−2. However, there are only three toes in the pes, which has a phalangeal formula of X−3−3/4−3/4−X. Importantly, the number of phalanges in the third and fourth pedal digits can vary between either three or four per digit, even within the same specimen. The Alag Teeg site has yielded as many as a hundred skeletons of the ankylosaur Pinacosaurus, most of which were immature when they died. Each skeleton is preserved in an upright standing position, with the bones of the lower limbs often in articulation. The remainder of the skeleton, including the upper parts of the limbs, is generally disarticulated and somewhat scattered. Based on the presence of large numbers of juvenile Pinacosaurus specimens at Alag Teeg, as well as other Djadokhta−age sites (Ukhaa Tolgod in Mongolia, Bayan Mandahu in China), it seems juvenile Pinacosaurus were probably gregarious

A reevaluation of the hyoid bones of protoceratops andrewsi granger and gregory, 1923 (ornithischia: Ceratopsia) and a review of hyoid elements in ornithischian dinosaurs

We present a reinterpretation of the bones previously identified as ossified hyoid elements in the Asian Late Cretaceous ceratopsian dinosaur Protoceratops andrewsi Granger and Gregory, 1923. Comparisons with other ceratopsian skeletons indicate that the tetraradiate bone tentatively regarded as a first ceratobranchial is actually an incomplete middle cervical rib, and the larger, flattened elements identified as second ceratobranchials are partial sternal plates. As in nearly all other ornithischian dinosaurs for which this area of the skeleton is known, the ossified hyoid apparatus of P. andrewsi probably consisted of a pair of rod-like first ceratobranchials; two additional, splint-like or sheet-like bones that are most frequently interpreted as ceratohyals may also have been present