A new order of tertiary zalambdodont marsupials.

Yalkaparidon coheni and Yalkaparidon jonesi are described here as the first-known members of the marsupial family Yalkaparidontidae and order Yalkaparidontia. Before discovery of these zalambdodont marsupials in unnamed Tertiary sediments from northwestern Queensland, only five orders of australidelphian marsupials were known. Dental and basicranial morphology suggest that notoryctids and yalkaparidontids, which both have highly specialized zalambdodont molars, are dentally convergent. Yalkaparidontids lived in lowland rainforests of northern Australia and appear to have vanished, with the rainforests, sometime in the middle to late Tertiary. Discovery of yalkaparidontids demonstrates a significantly greater breadth of diversity for Australian marsupials.