Introduction: The Marsupials

Abstract

The marsupials or pouched mammals form a distinctive group within the Class Mammalia. Though clearly possessing the diagnostic features of typical mammals, including high and stable body temperature, furry pelt, simple lower jaw and mammary glands, they have for long been accepted as standing apart from the main body of the Class. Generally thought of as ‘primitive’ (that is, displaying archetypal features which more advanced mammals have lost), they are considered to stand closer to placental mammals than to egg-laying monotremes or to the earlier forms — triconodonts, docodonts and multituberculates — known only as Mesozoic or early Tertiary fossils. This recognition is reflected in their taxonomic position. Though there is considerable taxonomic disagreement over the number of subclasses into which the Class Mammalia may properly be divided, most of the argument concerns the status of the early fossil groups; Simpson’s (1945) classification, which includes the marsupials and placentals in a single subclass Theria, is generally accepted. Marsupials form the Infraclass Metatheria, placentals the Infraclass Eutheria. Both groups made their first appearance in the Cretaceous, derived from pantotherian (trituberculate) stock of the Upper Jurassic.

Dr. Bernard Stonehouse was formerly a Reader in Zoology in the University of Canterbury, Christchurch, New Zealand, where his research included studies of introduced marsupials in forest and grassland habitats.