Description of new cranial material of 'Propalorchestes' (Marsupialia: Palorchestidae) from the Middle Miocene Camfield Beds, Northern Territory, Australia

Abstract

Additional material referable to Propalorchestes novaculacephalus from the middle Miocene Camfield Beds is described. A cranium prepared in 1999-2000 from material collected on the T H Rich expedition of 1981 represents the most complete skull of the genus found to date. The detailed preservation of the previously unknown rostral anatomy supports the hypothesis that 'Propalorchestes' possessed retracted nasal morphology. Cheek teeth from the skull and an additional isolated mandibular fragment from the same site, adds to the dental record for the genus. It further supports the intermediate condition of the molar morphology between the fully bilophodont 'Palorchestes' and the subselenodont/semilophodont wynyardiid morphologies. The highly retracted nasal morphology and corresponding mandibular features demonstrate an advanced and highly derived condition in contrast to the plesiomorphic features previously described for the basicranium. In comparison to the generalized rostral anatomy of the sister group, the early to middle Miocene Diprotodontidae, this more complete record of 'Propalorchestes' cranial morpholgy, suggests a significantly earlier origin for the highly derived facial anatomy in the Palorchestidae.