RESUMEN
The crocodylian fossil record from the Cenozoic of Australasia is notable for its rich taxonomic diversity, and is primarily represented by members of the clade Mekosuchinae. Reports of crocodylian fossils from Australia date back to the late nineteenth century. In 1886, Charles Walter de Vis proposed the name Pallimnarchus pollens for crocodylian fossils from southeast Queensland-the first binomen given to an extinct crocodylian taxon from Australia. Pallimnarchus has come to be regarded as a large, broad-snouted crocodylian from Australia's Plio-Pleistocene, and numerous specimens, few of which are sufficiently complete, have been assigned to it by several authors throughout the twentieth century. In the late 1990s, the genus was expanded to include a second species, Pallimnarchus gracilis. Unfortunately, the original syntype series described as Pallimnarchus pollens is very fragmentary and derives from more than one taxon, while a large part of the subsequently selected lectotype specimen is missing. Because descriptions and illustrations of the complete lectotype do not reveal any autapomorphic features, we propose that Pallimnarchus pollens should be regarded as a nomen dubium. Following this decision, the fossil material previously referred to Pallimnarchus is of uncertain taxonomic placement. A partial skull, formerly assigned to Pallimnarchus pollens and known as 'Geoff Vincent's specimen', possesses many features of diagnostic value and is therefore used as basis to erect a new genus and species-Paludirex vincenti gen. et sp. nov. A comprehensive description is given for the osteology of 'Geoff Vincent's specimen' as well as aspects of its palaeoneurology, the latter being a first for an extinct Australian crocodyliform. The newly named genus is characterized by a unique combination of premaxillary features such as a distinctive arching of the anterior alveolar processes of the premaxillae, a peculiar arrangement of the first two premaxillary alveoli and a large size disparity between the 3rd and 4th premaxillary alveoli. These features presently allow formal recognition of two species within the genus, Paludirex vincenti and Paludirex gracilis comb. nov., with the former having comparatively more robust rostral proportions than the latter. The Paludirex vincenti holotype comes from the Pliocene Chinchilla Sand of the Darling Downs, south-eastern Queensland, whereas the material assigned to Paludirex gracilis is from the Pleistocene of Terrace Site Local Fauna, Riversleigh, northwest Queensland. Phylogenetic analyses recover Paludirex vincenti as a mekosuchine, although further cladistic assessments are needed to better understand the relationships within the clade.
RESUMEN
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.
RESUMEN
While the crocodyliform lineage extends back over 200 million years (Myr) to the Late Triassic, modern forms-members of Eusuchia-do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea. Fossils of non-crocodylian eusuchians are currently rare and, in most instances, fragmentary. Consequently, the transition from Neosuchia to Crocodylia has been one of the most poorly understood areas of crocodyliform evolution. Here we describe a new crocodyliform from the mid-Cretaceous (98-95 Myr ago; Albian-Cenomanian) Winton Formation of Queensland, Australia, as the most primitive member of Eusuchia. The anatomical changes associated with the emergence of this taxon indicate a pivotal shift in the feeding and locomotor behaviour of crocodyliforms-a shift that may be linked to the subsequent rapid diversification of Eusuchia 20 Myr later during the Late Cretaceous and Early Tertiary. While Laurasia (in particular North America) is the most likely ancestral area for Crocodylia, the biogeographic events associated with the origin of Eusuchia are more complex. Although the fossil evidence is limited, it now seems likely that at least part of the early history of Eusuchia transpired in Gondwana.
