The periotic bones of possums and cuscuses: cuscus polyphyly and the division of the marsupial family Phalangeridae

Abstract

Detailed examination of the periotic bones of ten species of phalangerid marsupials revealed the existence of three distinctive classes of periotic morphology, termed ailuropine, trichosurin and phalangerin. Cladistic analysis of fifteen characters of the periotic suggested the ailuropine periotic to be the most plesiomorphic in morphology, with the trichosurin and phalangerin periotics representing a more derived clade. This character distribution would support recent taxonomic schemes, in which the cuscuses are seen as a paraphyletic grouping: the greater and lesser Sulawesi cuscuses (Ailurops ursinus and Strigocuscus celebensis) exhibiting respectively ailuropine and trichosurin periotics, with all other cuscuses possessing phalangerin periotics. However, it does not support the assertions of some authors that the Moluccan cuscuses (Phalanger ornatus and P. rothschildi) and the ground cuscus (P. gymotis) are trichosurins.