Petauridae Bonaparte, 1832

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 : 244-246

Petauridae Bonaparte, 1832

CONTENTS: Dactylonax , Dactylopsila , Gymnobelideus , and Petaurus (fig. 50).

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

CROWN AGE: 18.8 Mya (95% HPD: 15.9–22.4 Mya).

UNAMBIGUOUS CRANIODENTAL SYNAPOMORPHIES: None.

COMMENTS: Monophyly of Petauridae is strongly supported in our molecular (figs. 27–29) and total-evidence (figs. 32, 33) analyses, but we conspicuously failed to identify any unambiguous craniodental synapomorphies for the family. Instead, petaurids apparently retain the plesiomorphic states for many characters that evolved derived conditions along the branch leading to its sister taxon, Pseudocheiridae . 35 Nevertheless, five craniodental features optimize as petaurid synapomorphies under Accelerated Transformation only: the foramen rotundum is laterally exposed and separate from the sphenorbital fissure (char. 17: 1→0; ci = 0.286); postorbital processes are present (char. 18: 0→1; ci = 0.042); the frontal and squamosal are in contact on the lateral aspect of braincase (char. 26: 0→1; ci = 0.071); the presphenoid is exposed in the roof of the nasopharyngeal fossa above the posterior palate (char. 43: 1→0; ci = 0.091); the major crest of the semisectorial or fully sectorial P3 is oriented posterolabial to anterolingual (char. 127: 1→2; ci = 0.400); and the cristid obliqua of m1 contacts the metacristid labial to the metaconid (char. 169: 0→1; ci = 0.250).

Phylogenetic analyses of the fossil petauroid † Djaludjangi yadjana (not included in our analyses as it is known from partial dentitions only) suggests that certain dental features of petaurids reconstructed here as plesiomorphic, such as the absence of any trace of selenodonty, may in fact be secondary reversals ( Brammall, 1998). Archer (1984c: fig. 189), Archer et al. (1987), and Brammall (1998) listed a number of putative morphological synapomorphies for Petauridae , but, in general, we did not find these to be amenable for scoring as discrete characters. There is a pressing need for detailed studies of fossil and Recent phalangeridans to unravel patterns of craniodental evolution, because it seems plausible that “possum” evolution has been characterized by secondary simplification of certain features (including possible loss of selenodonty in petaurids) as well as the more widely recognized appearance of morphological novelties ( Winge, 1941; Archer, 1976e; Archer et al., 1987; Woodburne et al., 1987a; Springer and Woodburne, 1989; Brammall, 1998).

Within Petauridae , all our molecular (figs. 27–29) and total-evidence (figs. 32, 33) analyses placed Gymnobelideus in a clade with the dactylopsilines Dactylopsila and Dactylonax , to the exclusion of Petaurus . This arrangement was also recovered by the molecular analyses of Meredith et al. (2009a) and May-Collado et al. (2015), whereas the molecular analyses of Mitchell et al. (2014) and Álvarez-Carretero et al. (2021) found a Petaurus + Gymnobelideus clade. The cause of this incongruence between studies is unclear, and these different resolutions have important implications for the evolution of gliding adaptations (present in Petaurus and Gymnobelideus , absent in dactylopsilines) within Petauridae . The topology favored here implies that Gymnobelideus and Petaurus evolved their gliding patagia independently, or (perhaps less likely) that dactylopsilines have secondarily lost patagia. 36

Fossil petaurids have been reported from Oligo-Miocene sites in Australia, but much of this material remains undescribed ( Brammall, 1998; Archer et al., 1999; Archer and Hand, 2006). † Djaludjangi yadjana , mentioned above, shares some putative synapomorphies with petaurids, but this has not been tested via suitably comprehensive phylogenetic analysis († Djaludjangi was included in the analyses of Roberts, 2008, but these were specifically focused on relationships within Pseudocheiridae ), and Brammall’s (1998) recommendation that this taxon be treated as Petauroidea incertae sedis has been followed by subsequent authors ( Long et al., 2002; Archer and Hand, 2006; Black et al., 2012b).

Tedford et al. (1975) identified fragmentary craniodental remains, including two molars, from the early Miocene Geilston Bay Local Fauna of Tasmania ( Tedford et al., 1975; Tedford and Kemp, 1998; Black et al., 2012b; Woodhead et al., 2014) as representing a probable phalangerid, but Tedford and Kemp (1998) subsequently referred them to Petauroidea . Crosby et al. (2001) argued that these molars more likely represent a phalangerid based on the presence of well-developed lophs, but Roberts (2008) continued to refer to them as petauroid, although her phylogenetic analyses did not unambiguously support petauroid affinities for them. Also of interest is Hocknull’s (2005, 2009) report of a new, currently unnamed petaurid from middle Pleistocene deposits at Mount Etna in Queensland that appears to retain several dental plesiomorphies relative to Recent petaurids; future phylogenetic analyses including this taxon may help clarify relationships both within the family and between petaurids and other petauroids.