Macropodoids from the Middle Miocene Namba Formation, South Australia, and the homology of some dental structures in kangaroos

Abstract

Macropodoids from the Tarkarooloo local fauna, including Nambaroo tarrinyeri n. gen. and sp., N. saltavus n. sp., N. novus n. sp. and Palaeopotorous priscus n. gen. and sp., include the most plesiomorphic macropodids and potoroids known. Together with the newly discovered macropodoids from the Pinpa and Yanda local faunas they are also the oldest macropodoids described. Study of the morphology of these plesiomorphic macropodoids indicates that the trigonid of the M2 in potoroids and macropodids is composed of different structures (the protoconid and metaconid in macropodids and the protoconid and protostylid in potoroids). Also, the posterior cingulum in macropodids is a neomorphic structure, and not homologous with the posterior cingulum (the posthypocristid and postentocristid) in potoroids and phalangerids. A unique M2 trigonid configuration, where the cristid obliqua connects with the protostylid, is here recognized as being present in plesiomorphic macropodoids and phalangerids, and possibly represents a synapomorphy for a clade containing members of those groups.