Minmi

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: The diet of fossil vertebrates is usually inferred from the forms of the teeth, sometimes assisted by an analysis of the jaw mechanics. Although generally useful for distinguishing carnivores from herbivoresexcept for a few cases where the teeth reliably reflect a specific food, such as for fish-eating pterosaurs-this method doesn't identify either the taxa or structures eaten. Coprolites are more revealing but rare, and it is often difficult to attribute them to specific taxa. Cololites (gut contents: Hunt, 1992) are also rare, but provide the most reliable identification of dietary items to specific taxa. One such example is the contents of the gut preserved in a specimen of the small Early Cretaceous Australian armoured dinosaur, Minmi. This is the first report of a cololite for any thyreophoran dinosaur, and the most reliable report of dietary items for any specific herbivorous dinosaur. Cololites have been previously reported in hadrosaurs (Kriusel, 1922; Weigelt, 1927), but with some dissent (Abel, 1922; Currie, et al., 1996), and in sauropods (Stokes, 1964; Ash, et al., 1992). However, the alleged sauropod cololite is now thought to have been misidentified, and not to be of biogenic origin (Madsen, pers. comm., 1998; Currie, et al., 1996). Diets for dinosaurs, including thyreophorans, have been surveyed recently by Ryan and Vickaryous (1997), based on the work of Weishampel (1984). He concluded that thyreophorans probably fed on plants within 2 m of the ground, limited oral processing to crushing and slicing or puncturing, and may have fed on "the fleshy components of bennettitalian, nilssonialian ... [and] caytonialian inflorescences ... and angiosperm fructifications" (Weishampel, 1984:172). Ankylosaurs, although generally considered herbivores, have also been interpreted as insectivores (Nopcsa, 1928). This opinion is now widely considered unlikely, and the view of Haas (1969) that ankylosaurs fed on soft (i.e., non-abrasive) plants or plant materials is more generally accepted. Dettmann, et al. (1992:248) hazarded the opinion that Minmi might have fed on "water fern or other macrophyte vegetation." In 1990 the Queensland Museum collected an ankylosaur skeleton from the Toolebuc Formation (Albian) in north-central Queensland, Australia. The specimen (Queensland Museum F18101), attributed to Minmi sp., is an almost complete, articulated skeleton (Molnar, 1996), much of which was enclosed within what appears originally to have been a single, large calcareous nodule. In the process of removing the nodular matrix, a small variegated patch of material was found (Fig. 1).