Perameloidea Gray, 1825

Beck, Robin M. D., Voss, Robert S. & Jansa, Sharon A., 2022, Craniodental Morphology And Phylogeny Of Marsupials, Bulletin of the American Museum of Natural History 2022 (457), pp. 1-353 : 210-211

Perameloidea Gray, 1825

CONTENTS: Chaeropodidae , Peramelidae , and Thylacomyidae .

STEM AGE: 26.1 Mya (95% HPD: 20.7–31.8 Mya).

CROWN AGE: 20.0 Mya (95% HPD: 15.3–24.5 Mya).

UNAMBIGUOUS CRANIODENTAL SYNAPOMORPHIES: Nasals truncated anterior to lacrimals (char. 3: 0→1; ci = 0.333); lacrimal exposure on orbital rim forming a distinct crest (char. 8: 0→2; ci = 0.118); frontal and squamosal in contact on lateral aspect of braincase (char. 26: 0→1; ci = 0.071); palatine fenestrae present (char. 38: 0→1; ci = 0.071); posterior epitympanic sinus of squamosal present, enclosed laterally (char. 84: 0→1; ci = 0.071); and entocristid indistinct or absent (char. 176: 0→1; ci = 0.077).

COMMENTS: We follow Van Dyck and Strahan’s (2008) use of Perameloidea to refer only to the peramelemorphian crown clade, as did Kear et al. (2016). By contrast, other recent studies (e.g., Chamberlain et al., 2015; Warburton and Travouillon, 2016) have used Perameloidea to refer to the crown clade plus all taxa more closely related to it than to the fossil genus † Yarala , which has been placed in the family † Yaralidae and superfamily †Yaraloidea ( Muirhead, 2000; Warburton and Travouillon, 2016).

Within Perameloidea, all our molecular (figs. 27–29) and total-evidence (figs. 32, 33) analyses support Peramelidae and Macrotis (Thylacomyidae) as sister taxa, with Chaeropus (Chaeropodidae) the first perameloid family to diverge. This topology is congruent with most other recent molecular and totalevidence phylogenetic analyses ( Meredith et al., 2008a; Westerman et al., 2012; Kear et al., 2016; Travouillon and Phillips, 2018). However, the dated total-evidence analysis of Travouillon and Phillips (2018: figs. 1E, 2) placed Chaeropus sister to Macrotis , the dated total-evidence analyses of Travouillon et al. (2021) placed Thylacomyidae outside Chaeropus + Peramelidae , 31 and the molecular phylogenetic analyses of Travouillon et al. (2019) placed Chaeropus either sister to Isoodon + Perameles + Peroryctes (in an undated maximum likelihood analysis; Travouillon et al., 2019: fig. 15) or sister to Isoodon (in a Bayesian node-dating analysis; Travouillon et al., 2019: fig. 16).

We identified a number of unambiguous cranidodental synapomorphies as characterizing Perameloidea, although most of these are homoplastic. Perhaps the most notable of these is truncation of the nasals anterior to the lacrimals, a trait that is present in all known perameloids (and arose homoplastically in Notoryctes and Potorous ) but that is absent in nonperameloid peramelemorphians, all of which are “short-snouted” ( Travouillon et al., 2010, 2013b, 2015b; Gurovich et al., 2014; Chamberlain et al., 2015).

The oldest putative perameloid is † Bulbadon warburtonae from the late Oligocene Ditjimanka Local Fauna (Faunal Zone B) of the Etadunna Formation, which is known from a single partial mandible, and has been tentatively identified as a thylacomyid ( Travouillon et al., 2021). A best-fit age-model of paleomagnetic data indicates that the Etadunna Formation spans 23.6–26.1 Mya ( Metzger and Retallack, 2010), so, if † Bulbadon is a thylacomyid, then it predates our estimate for the crown age of Perameloidea. However, † Bulbadon did not form a clade with other thylacomyids in the dated total-evidence analyses of Travouillon et al. (2021) and a lack of resolution meant that a position for † Bulbadon outside Perameloidea could not be ruled out in their analyses. Two taxa from the middle Miocene of Riversleigh World Heritage Area, both known only from isolated teeth, may also be early perameloids ( Travouillon et al., 2014a): † Crash bandicoot (which appears to be a peramelid), and † Liyamayi dayi (which was described as a thylacomyid, although its position in published phylogenies is highly labile; Travouillon et al., 2014 a, 2015 b, 2021; Chamberlain et al., 2015; Kear et al., 2016). If † Crash and † Liyamayi are indeed early perameloids, then their middle Miocene age is broadly congruent with our middle to early Miocene age estimate for the onset of diversfication of Perameloidea.