Pseudocheiridae Winge, 1893

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 : 246-248

Pseudocheiridae Winge, 1893

CONTENTS: Petauroides , Petropseudes , Pseudocheirus , Pseudochirops (fig. 51), and Pseudochirulus .

STEM AGE: 24.4 Mya (95% HPD: 23.6–26.1 Mya).

CROWN AGE: 15.8 Mya (95% HPD: 11.7–18.5 Mya).

UNAMBIGUOUS CRANIODENTAL SYNAPOMOR- PHIES: Paroccipital process a large erect process usually directed ventrally (char. 93: 1→2; ci = 0.100); mandible usually with two or more mental foramina (char. 98: 0→1; ci = 0.063); P2 “pseudocheiriform” (char. 118: 0→1; ci = 0.444); P3

semisectorial (char. 123: 0→1; ci = 0.385); paracone not completely fused with any stylar elements (char. 136: 2→0; ci = 0.250); principal labial and lingual cusps of upper molars not connected by transverse lophs (char. 144: 1→0; ci = 0.200); additional cuspid labial to m1 present, forming a cusplike protostylid (char. 165: 0→1; ci = 0.286); entocristid well labial of the lingual margin (char. 177: 0→1; ci = 0.250); and hypoconulid present (char. 178: 1→0; ci = 0.333).

COMMENTS: Monophyly of Pseudocheiridae is strongly supported by our molecular (figs. 27–29), morphological (fig. 30, 31), and totalevidence (figs. 32, 33) analyses, and this clade is associated with a correspondingly long list of unambiguous craniodental (but mostly dental) synapomorphies. This impressive character support is in stark contrast with the previously discussed lack of morphological support for Petauridae and with the unpublished results of Roberts’ (2008) analyses. Because the last incorporated numerous fossil pseudocheirids (some of which are known from relatively complete, but currently unpublished, cranial material), it seems likely that adding these and other key fossil petauroids (such as † Djaludjangi ) to future totalevidence analyses will have a major impact on character polarity within Petauroidea (see discussions in Winge, 1941; Archer, 1976e; Archer et al., 1987; Flannery, 1987; Woodburne et al., 1987a, 1987b; Springer and Woodburne, 1989; Brammall, 1998). Within Pseudocheiridae , we find support for the same three subfamilies— Hemibelideinae ( Hemibelideus and Petauroides ), Pseudocheirinae ( Pseudocheirus and Pseudochirulus ), and Pseudochiropsinae ( Pseudochirops and Petropseudes )—that have also been supported in recent molecular studies (Meredith et al., 2009a, 2010; Mitchell et al., 2014; May-Collado et al., 2015; Álvarez-Carretero et al., 2021).

Fossil pseudocheirids are first known from the late Oligocene of Australia ( Woodburne et al., 1987b; Bassarova and Archer, 1999; Roberts, 2008; Roberts et al., 2009). However, based on largely on the results of recent revisionary work by Roberts (see also Bassarova and Archer, 1999; Long et al., 2002; Archer and Hand, 2006), the oldest definitive crown-clade pseudocheirids currently known appear to be early Pliocene, namely Pseudochirops † winteri from the Bluff Downs Local Fauna (Mackness and Archer, 2001) and Pseudocheirus † marshalli and Petauroides † stirtoni from the ~4.46 Mya Hamilton Local Fauna ( Turnbull and Lundelius, 1970; Archer, 1984c; Turnbull et al., 1987; Bassarova and Archer, 1999; Turnbull et al., 2003), with Petauroides † stirtoni possibly also present in the early Pliocene Big Sink Fauna (Dawson et al., 1999). This is broadly congruent with our estimated divergence dates, in which crown-clade Pseudocheiridae is inferred as having begun to diversify during the early or middle Miocene.