Do Phalangeriforms (Marsupialia: Diprotodontia) Have a 'hypocone'?

Abstract

The identity of some molar cusps of phalangeriform marsupials has been debated, particularly the distolingual cusp of the upper molars, called the metaconule or hypocone by different workers. Here, we examine the molar teeth of two eutherian and two phalangeriform taxa to reconstruct the positions of cusps and crests during the masticatory cycle. The major cusp on the distolingual corner of the upper cheek teeth of Trichosurus and Pseudocheirus occludes with lower molars in a manner analogous to the hypocone of Saimiri (Recent, Eutheria, Primates), and not to the metaconule of Didelphodus (Eocene, Eutheria, Insectivora). Both topographical and functional criteria support the identification of the distolingual cusp of the upper molar of phalangeriforms as a hypocone rather than a metaconule as previously proposed.