Fossil evidence in Australia for oldest known freshwater crayfish of Gondwana

Early Cretaceous body and trace fossils in Victoria, Australia, establish the oldest known presence of parastacid crayfish (Decapoda: Astacidea, Parastacoidea) in freshwater environments of Australia, and the oldest known crayfish in Gondwana. Parastacid body fossils, comprised of a partial abdomen (Palaeoechinastacus australianus, gen. et sp. nov.) and two chelae, are from a fluvial deposit in the Otway Group (Albian). Trace fossils in fluvial deposits of the Otway Group and Strzelecki Group (Aptian) also closely resemble modern parastacid burrow systems, supplying independent verification of crayfish presence and their burrowing habits in Australia at this time. Paleoenvironments in this region were high-latitude and periglacial, indicating that these crayfish were adapted to cold-water ecosystems. The combined fossil evidence provides a starting point for the previously unknown paleoecology and evolutionary history of Mesozoic parastacids in Australia, while supporting phylogenies that suggest parastacid radiation from southeastern Australia before the complete breakup of Gondwana

Second specimen of Corriebaatar marywaltersae from the Lower Cretaceous of Australia confirms its multituberculate affinities

A second specimen of the Australian cimolodontan multituberculate Corriebaatar marywaltersae from the same locality (Flat Rocks) as the holotype and previously only known specimen, reveals far more anatomical information about the species. The new specimen, composed of most of a dentary containing a complete p4 and alveoli for the lower incisor and the lower first and second molars, exhibits a suite of features consistent with allocation of Corriebaatar to Cimolodonta and further confirms the presence of multituberculates on Gondwana during the Mesozoic. The revised (older) age of the Flat Rocks locality to latest Barremian (mid-Early Cretaceous) establishes C. marywaltersae as the oldest currently known cimolodontan. This has profound biogeographic implications for the distribution of multituberculates on Gondwana as well as globally, particularly in light of the fact that Corriebaatar appears to be a relatively derived member of Cimolodonta

The mandible and dentition of the Early Cretaceous monotreme Teinolophos trusleri

The monotreme Teinolophos trusleri Rich, Vickers-Rich, Constantine, Flannery, Kool & van Klaveren, 1999 from the Early Cretaceous of Australia is redescribed and reinterpreted here in light of additional specimens of that species and compared with the exquisitely preserved Early Cretaceous mammals from Liaoning Province, China. Together, this material indicates that although T. trusleri lacked a rod of postdentary bones contacting the dentary, as occurs in non-mammalian cynodonts and basal mammaliaforms, it did not share the condition present in all living mammals, including monotremes, of having the three auditory ossicles, which directly connect the tympanic membrane to the fenestra ovalis, being freely suspended within the middle ear cavity. Rather, T. trusleri appears to have had an intermediate condition, present in some Early Cretaceous mammals from Liaoning, in which the postdentary bones cum ear ossicles retained a connection to a persisting Meckel’s cartilage although not to the dentary. Teinolophos thus indicates that the condition of freely suspended auditory ossicles was acquired independently in monotremes and therian mammals. Much of the anterior region of the lower jaw of Teinolophos is now known, along with an isolated upper ultimate premolar. The previously unknown anterior region of the jaw is elongated and delicate as in extant monotremes, but differs in having at least seven antemolar teeth, which are separated by distinct diastemata. The dental formula of the lower jaw of Teinolophos trusleri as now known is i2 c1 p4 m5. Both the deep lower jaw and the long-rooted upper premolar indicate that Teinolophos, unlike undoubted ornithorhynchids (including the extinct Obdurodon), lacked a bill.The Committee for Research and Exploration of the National Geographic Society and the Australian Research Council provided much of the funding needed for the fieldwork carried out at the Flat Rocks locality. We acknowledge travel funding provided by the International Synchrotron Access Program managed by the Australian Synchrotron and funded by the Australian Government