Craniodental Morphology And Phylogeny Of Marsupials Author Beck, Robin M. D. School of Science, Engineering and Environment University of Salford, U. K. & School of Biological, Earth & Environmental Sciences University of New South Wales, Australia & Division of Vertebrate Zoology (Mammalogy) American Museum of Natural History Author Voss, Robert S. Division of Vertebrate Zoology (Mammalogy) American Museum of Natural History Author Jansa, Sharon A. Bell Museum and Department of Ecology, Evolution, and Behavior University of Minnesota text Bulletin of the American Museum of Natural History 2022 2022-06-28 2022 457 1 353 https://bioone.org/journals/bulletin-of-the-american-museum-of-natural-history/volume-457/issue-1/0003-0090.457.1.1/Craniodental-Morphology-and-Phylogeny-of-Marsupials/10.1206/0003-0090.457.1.1.full journal article 10.1206/0003-0090.457.1.1 0003-0090 6971356 Vombatidae Burnett, 1830 CONTENTS: Lasiorhinus , Vombatus (fig. 45), and † Warendja . STEM AGE: 22.3 Mya (95% HPD: 17.0–27.9 Mya). CROWN AGE: 11.4 Mya (95% HPD: 3.7–19.1 Mya). UNAMBIGUOUS CRANIODENTAL SYNAPOMORPHIES: Masseteric process absent (char. 6: 1→0; ci = 0.125); hypotympanic sinus floor formed by squmosal only (char. 56: 0→1; ci = 0.667); postglenoid process of squamosal absent (char. 75: 0→1; ci = 0.200); P3 open-rooted (char. 123: 1→3; ci = 0.385); and molars with open roots, the crowns growing throughout adulthood (char. 128: 0→1; ci = 1.000). FIG. 45. Vombatus ursinus ( Diprotodontia , Vombatidae ; based on AMNH 200456, an adult of unknown sex from Tasmania, with missing dental elements reconstructed from AMNH 65622, an adult female from Tasmania). COMMENTS: All our morphological, molecular, and total-evidence analyses recover monophyly of Vombatidae ( figs. 27–33 ). We have included only hypselodont vombatids among our terminals, and hence the presence of open-rooted P3 and open-rooted molars optimize as unambiguous synapomorphies for the family; however, putative vombatids with rooted P3 and rooted molars are known ( Stirton et al., 1967b ; Murray, 1998 ; Brewer, 2008 ; Brewer et al., 2008 , 2015 , 2018 ), so the inclusion of such plesiomorphic taxa in future analyses may erode dental character support for the family. The other two unambiguous craniodental synapomorphies identified here are in the glenoid region (namely absence of a masseteric process and absence of a postglenoid process of the squamosal) and are presumably correlated with the unusual masticatory pattern of hypselodont vombatids, in which jaw movement during the power stroke of mastication is primarily or exclusively transverse ( Ferreira et al., 1989 ; Murray, 1998 ; Crompton et al., 2008 ; Brewer et al., 2015 ). The oldest vombatids known from dental material (the early Miocene † Nimbavombatus and † Rhizophascolonus ; Stirton et al., 1967b ; Murray, 1998 ; Brewer et al., 2008 , 2015 , 2018 ) are not hypselodont, and they appear to have had an orthal component to their power stroke; however, the morphology of the glenoid region of these taxa, which might be expected to be less specialized than those of hypselodont vombatids, is currently unknown. Our estimate for the divergence between † Warendja and extant vombatids ( Vombatus and Lasiorhinus ) is poorly constrained, with the 95% HPD extending into the Pliocene; this raises the possibility that the late Miocene † Warendja encorensis may not belong to this genus (see Brewer et al., 2007 , 2018 : fig. 19).