A morphological analysis of marsupial mammal higher-level phylogenetic relationships
Inés Horovitza,* and Marcelo R. Sánchez-Villagrab
aNatural History Museum of Los Angeles County, Section of Mammalogy, 900 Exposition Boulevard, Los Angeles, CA 90007, USA
bZoologisches Institut, Universität Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany
Phylogenetic relationships among marsupial taxa have proven to be more complex than the simple grouping of species by continent. Recent marsupials are distributed across the New World, Australia, New Guinea, and certain neighbouring islands. Morphological characteristics of various groups bridge diﬀerent geographical areas. We investigated the origin of these characteristics by assembling a morphological data matrix consisting of a new suite of 149 postcranial characters and incorporated a series of previously published data on the craniodental (76 characters) and soft tissue (5 characters) anatomy. Twenty-one marsupial terminal taxa representing all the major radiations of marsupials and 10 outgroups, most of which are exceptionally well-preserved fossils such as Vincelestes, Ukhaatherium, and a few basal metatherian taxa, were investigated. A maximum parsimony analysis was conducted, resulting in one most parsimonious tree. Relationships among outgroups are congruent with current understanding of mammalian phylogeny. All currently accepted marsupial orders were recovered by the analysis. We conﬁrmed previous results showing the South American ‘‘monito del monte’’ Dromiciops nested within the Australasian radiation. Within this australidelphian clade, Dromiciops was closely allied with the Diprotodontia. The South American paucituberculates appeared more closely related to the Australidelphia than to the American Didelphimorphia. The marsupial mole Notoryctes and the Peramelia were closely allied to each other and in turn were the sister group of the Dromiciops plus Diprotodontia clade. This pattern of relationships left Dasyuromorphia as the most basal oﬀshoot of the Australidelphia. Whereas this tree topology recovers some signal that had been detected by previous studies, morphological and/or molecular, some novel hypotheses are also supported.