Balbaridae Kear and Cooke, 2001

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 : 251-252

† Balbaridae Kear and Cooke, 2001

CONTENTS: † Balbaroo and † Ganawamaya .

STEM AGE: 27.7 Mya (95% HPD: 23.6–32.1 Mya).

CROWN AGE: 22.5 Mya (95% HPD: 18.7–27.3 Mya).

UNAMBIGUOUS CRANIODENTAL SYNAPOMORPHIES: Mandible usually with two or more mental foramina (char. 98: 0→1; ci = 0.063), distinct posterolingual cusp on semi- or fully sectorial P3 present (char. 125: 0→1; ci = 0.200); principal labial and lingual cusps of upper molars connected by well-developed lophs (char. 144: 1→2; ci = 0.200); and midpoints of protoloph and metaloph connected by a “midlink” (char. 145: 0→1; ci = 0.500)

COMMENTS: The first balbarids to be described, namely † Balbaroo camfieldensis and † B. gregoriensis , were originally referred to Macropodidae based largely on their fully lophodont molars ( Flannery et al., 1983). However, Cooke (1997a, 1997 b, 1997c) showed that balbarids and macropodids appear to have evolved lophodonty independently, and Kear and Cooke (2001) subsequently recognized † Balbaridae as a distinct family.

The position of † Balbaridae has varied in published morphological and total-evidence phylogenetic analyses, and the family has not always been recovered as monophyletic ( Kear et al., 2007; Kear and Pledge, 2008; Black et al., 2014c; Travouillon et al., 2014b, 2015 a, 2016; Cooke et al., 2015; Butler et al., 2016, 2018; Cascini et al., 2019). However, both of our total-evidence analyses (figs. 32, 33) support balbarid monophyly. A position for † Balbaridae outside Macropodidae + Potoroidae in our dated analysis ( fig. 33) is due to the use of topological constraints required to calibrate selected nodes within Macropodiformes. These constraints may have influenced the character optimizations that indicate that presence of welldeveloped lophs connecting the principal labial and lingual cusps of the upper molars, and the presence of a midlink connecting these lophs, are both unambiguous synapomorphies of † Balbaridae . Nevertheless, these optimizations are congruent with Cooke’s (1997a, 1997 b, 1997c) hypothesis that balbarids acquired fully lophodont molars independently of macropodids.

Balbarids were relatively diverse during the late Oligocene, but appear to have declined in diversity from the early Miocene onward, with their last records coming from the late middle or early late Miocene (Faunal Zone D) Encore site at Riversleigh World Heritage area ( Butler et al., 2017).