Ausktribosphenidae is a group name that has been given to some rather puzzling fossils which: * appear to have tribosphenic molars, a type of tooth which is otherwise known only in Therians. * come from mid Cretaceous deposits in Australia - but Australia was connected only to Antarctica, and placentals originated in the northern hemisphere and were confined to it until continental drift formed land connections from North America to South America, from Asia to Africa and from Asia to India (the late Cretaceous map at [1] shows how the southern continents are separated. * are represented only by skull and jaw fragments, which are not very helpful.