THE POSTCRANIAL SKELETON OF THE MIOCENE KANGAROO, HADRONOMAS-PUCKRIDGI WOODBURNE (MARSUPIALIA, MACROPODIDAE)

Hadronomas was a large kangaroo similar in size to Simosthenurus occid entalis. Its pes was relatively long and robust, resembling those of t he sthenurines Procoptodon and Sthenurus in possessing ligamentous spe cialisations of the fourth proximal phalanx, anteroposterior compressi on of fourth proximal and median phalanges, broad, blunt 'hoof-like' t erminal fourth phalanx, a shallow calcaneocuboidal 'step', anteroposte rior as opposed to mediolateral differentiation of the ankle joint, hi gh, rounded profile of the astragalar trochleae and a reduced, mediall y situated proximal ventromedial facet of the cuboid. The upper and lo wer limb girdles resemble those of sthenurines in that the coracoverte bral angle of the scapula is elevated and produced anteriorly in the f orm of a rectangular process. The innominate is anteroposteriorly broa d and the ischium is flattened in cross section. The tibia possesses a sinuous shaft and an elongated, smoothly convex tibial crest that tap ers gradually into the diaphysis. Hadronomas's postcranial skeleton di ffers from other sthenurines in retaining a large functional fifth dig it and in showing no proximodistal compression of the cuboid. A charac ter analysis of the postcranial skeleton of Hadronomas indicates that the genus represents a primitive member of the Sthenurinae, and that t he Sthenurinae and the Macropodinae diverged at an early stage in macr opodid evolution.