Evolution, Biogeography and Palaeoecology of The Ornithorhynchidae.

Abstract

This paper reviews present understanding of the evolution of the ornithorhynchids. An ancient family within the mammalian order Monotremata. Ornithorhynchidae today is represented only by the living platypus Ornithorhynchus analinus but has a history that probably predates the Tertiary and a past distribution that spanned at least three continents. Analysis of the palaeontological record has focused on the distinctive ornithorhynchid dentition, which in species of Monotrematum and Obdurodon was probably functional throughout life. The retention of functional dentition in concert with the great age of Ornithorhynchidae gives the platypus family a much larger role in analysis of the biogeographic and phylogenetic history of the monotremes than is given to the more specialised, edentate tachyglossids, or echidnas. A complete ornithorhynchid skull, recovered from Miocene deposits at Riversleigh in north-western Queensland, has allowed comparison between the cranium of a generally more plesiomorphic platypus and that of the living Or. anatinus, a study that answers some of the morphological questions posed by this enigmatic group while raising others. This review concludes with a discussion of the biogeography and palaeoecology of the family.