Species Limits And Phylogenetic Relationships In The Didelphid Marsupial Genus Thylamys Based On Mitochondrial Dna Sequences And Morphology Author Giarla, T. C. Author Voss, R. S. Author Jansa, S. A. text Bulletin of the American Museum of Natural History 2010 2010-12-16 2010 346 1 67 journal article 0003-0090 Subgenus Thylamys Gray, 1843 TYPE SPECIES: Thylamys elegans ( Waterhouse, 1839 ) . CONTENTS: Seven species, as recognized below. REMARKS: Monophyly of the subgenus Thylamys is strongly supported by phylogenetic analyses of mtDNA sequence data ( fig. 11 ). Although none of the morphologi- cal traits that distinguish this subgenus from Xerodelphys (table 15) optimize as synapomorphies on the best current estimate of thylamyine relationships ( Voss and Jansa, 2009 : fig. 36), resolution of the still-uncertain relationships of Chacodelphys could change this situation. Because Chacodelphys , Lestodelphys , and Xerodelphys are all short-tailed taxa that lack a distinct caudal prehensile surface, phylogenies that include the nested clades ( Chacodelphys ( Lestodelphys ( Xerodelphys ( Thylamys )))) could constrain character optimizations such that a relatively long tail ( $ HBL) and well-developed caudal prehensile surface would be synapomorphic for the subgenus Thylamys .