Endocranium

Abstract: Skull anatomy other than the ear region of the pen-tailed treeshrew, Ptilocercus lowii Gray, 1848 (Ptilocercidae), is described and illustrated in detail based on 11 specimens from the Carnegie Museum of Natural History and the United States National Museum. Comparisons are made to the common treeshrew, Tupaia glis (Diard, 1820) (Tupaiidae), in a manner similar to the author's treatment of the ear region (Wible 2009). Included are bone by bone treatment of the external surfaces of the skull and hyoid apparatus, and composite treatment of the endocranium for P. lowii with comparisons to an uncertain species of Tupaia Raffles, 1821, and T. glis. The principal cranial foramina and their contents are addressed. Treeshrews are members of the placental order Scandentia, which is nested within the higher-level clade Euarchonta, along with the order Primates and the order Dermoptera (colugos). Relationships among these three orders are controversial in recent molecular studies, and detailed morphological...

Abstract: Minmi is the only known genus of ankylosaurian dinosaur from Australia. Seven specimens are known, all from the Lower Cretaceous of Queensland. Only two of these have been described in any detail: the holotype specimen Minmi paravertebra from the Bungil Formation near Roma, and a near complete skeleton from the Allaru Mudstone on Marathon Station near Richmond, preliminarily referred to a possible new species of Minmi. The Marathon specimen represents one of the world's most complete ankylosaurian skeletons and the best-preserved dinosaurian fossil from eastern Gondwana. Moreover, among ankylosaurians, its skull is one of only a few in which the majority of sutures have not been obliterated by dermal ossifications or surface remodelling. Recent preparation of the Marathon specimen has revealed new details of the palate and narial regions, permitting a comprehensive description and thus providing new insights cranial osteology of a basal ankylosaurian. The skull has also undergone computed tomography, digital segmentation and 3D computer visualisation enabling the reconstruction of its nasal cavity and endocranium. The airways of the Marathon specimen are more complicated than non-ankylosaurian dinosaurs but less so than derived ankylosaurians. The cranial (brain) endocast is superficially similar to those of other ankylosaurians but is strongly divergent in many important respects. The inner ear is extremely large and unlike that of any dinosaur yet known. Based on a high number of diagnostic differences between the skull of the Marathon specimen and other ankylosaurians, we consider it prudent to assign this specimen to a new genus and species of ankylosaurian. Kunbarrasaurus ieversi gen. et sp. nov. represents the second genus of ankylosaurian from Australia and is characterised by an unusual melange of both primitive and derived characters, shedding new light on the evolution of the ankylosaurian skull.

Abstract: A well-preserved neurocranium with attached partial skull roof is described from the Early Devonian Taemas Formation at Wee Jasper, southern New South Wales, Australia. The dermal ornament, skull roof pattern, and general proportion and structure of the endocranium are typically actinopterygian and the specimen is tentatively assigned to the actinopterygian genus Ligulalepsis. Other features more closely resemble some other groups, such as sarcopterygians (widely-spaced orbital walls, and short, broad telencephalon cavity), acanthodians (position of hyo-mandibular facet), and placoderms (many similarities including position of foramina for oculomotor, profundus, and trigeminal nerves, pituitary vein, and ophthalmic and orbital arteries in and around the orbit). This specimen is the first early osteichthyan to demonstrate the presence of an eyestalk, previously known only in placoderms and chondrichthyans. The unusual mix of characters and presence of an eyestalk provide new insights into primitiv...