Phascolarctomorphia Aplin and Archer, 1987

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 : 228-230

Phascolarctomorphia Aplin and Archer, 1987

CONTENTS: † Litokoala , † Nimiokoala , and Phascolarctos (fig. 44).

STEM AGE: 32.4 Mya (95% HPD: 29.1–36.4 Mya).

CROWN AGE: 25.3 Mya (95% HPD: 19.6–30.3 Mya).

UNAMBIGUOUS CRANIODENTAL SYNAPOMORPHIES: Extracranial course of mandibular nerve traverses a bony canal in the roof of the hypotympanic sinus (char. 52: 1→2; ci = 0.231); postgenoid vein emerges from the postglenoid foramen in the posteromedial corner of the glenoid fossa, medial or anteromedial to the postglenoid process (char. 77: 0→1; ci = 0.250); and additional cuspid labial to m1 protoconid present, forming a cusplike protostylid (char. 165: 0→1; ci = 0.286).

COMMENTS: Phascolarctidae is consistently recovered in our molecular, morphological and total-evidence analyses ( figs. 27–33 ) as sister to the remaining vombatiforms, which collectively comprise Vombatomorphia (note that we consider † Thylacoleonidae to be Diprotodontia incertae sedis and not a member of Vombatiformes; see above). Aplin and Archer (1987) placed Phascolarctidae in its own infraorder, Phascolarctomorphia (coordinate to Vombatomorphia), and it remains the only known phascolarctomorphian family; thus, the craniodental synapomorphies of Phascolarctidae apply equally to Phascolarctomorphia.

Known phascolarctids are craniodentally distinctive ( Sonntag, 1922; Archer, 1984a, 1984c; Aplin, 1987, 1990; Lee and Carrick, 1989; Springer and Woodburne, 1989; Black and Archer, 1997b; Louys et al., 2009; Black et al., 2014a), and monophyly of this clade is supported by three unambiguous craniodental synapomorphies in our analysis, although all show some degree of homoplasy. Perhaps the most striking of these is the extracranial course of the mandibular nerve, which traverses a bony canal in the roof of the hypotympanic sinus in all three of our phascolarctid terminals († Litokoala , † Nimiokoala and Phascolarctos ; Aplin, 1987; 1990; Louys et al., 2009), a feature that (as far as we are aware) occurs in no other metatherians. 34

In contrast to Black et al. (2012a), we found † Nimiokoala , rather than † Litokoala , to be more closely related to Phascolarctos , with the † Nimiokoala + Phascolarctos clade supported by a single unambiguous synapomorphy (see file S 3 in the online supplement): maxillary and frontal bones in contact on medial orbital wall (char. 13 0→1; ci = 0.143). Like other vombatiform families, the oldest record of Phascolarctidae is from late Oligocene sites in Australia ( Archer et al., 1999; Long et al., 2002; Archer and Hand, 2006; Black et al., 2012b, 2014b).

Figures

FIG. 27. Fifty-percent majority rule consensus of post-burn-in trees that results from Bayesian analysis of our nuclear sequence-only dataset. Black dots at nodes indicate ≥0.95 Bayesian posterior probability (“strong support”); dark gray dots indicate 0.75–0.94 Bayesian posterior probability (“moderate support”); light gray dots indicate 0.50–0.74 Bayesian posterior probability (“weak support”).

FIG. 28. Fifty-percent majority rule consensus of post-burn-in trees that results from undated Bayesian analysis of our mitochondrial sequence-only dataset. Black dots at nodes indicate ≥0.95 Bayesian posterior probability (“strong support”); dark gray dots indicate 0.75–0.94 Bayesian posterior probability (“moderate support”); light gray dots indicate 0.50–0.74 Bayesian posterior probability (“weak support”).

FIG. 29. Fifty-percent majority rule consensus of post-burn-in trees that results from undated Bayesian analysis of our combined nuclear and mitochondrial sequence dataset. Black dots at nodes indicate ≥0.95 Bayesian posterior probability (“strong support”); dark gray dots indicate 0.75–0.94 Bayesian posterior probability (“moderate support”); light gray dots indicate 0.50–0.74 Bayesian posterior probability (“weak support”).

FIG. 30. Strict consensus of 99,999 most parsimonious trees (each of 949 steps, consistency index =0.269, retention index = 0.815) that result from maximum parsimony analysis of our morphological dataset. Black dots at nodes indicate ≥70% bootstrap support (“strong support”); dark gray dots indicate 50%–69% bootstrap support (“moderate support”); light gray dots indicate <50 bootstrap support (“weak support”).

FIG. 31. Fifty-percent majority rule consensus of post-burn-in trees that results from undated Bayesian analysis of our morphological dataset. Black dots at nodes indicate ≥0.95 Bayesian posterior probability (“strong support”); dark gray dots indicate 0.75–0.94 Bayesian posterior probability (“moderate support”); light gray dots indicate 0.50–0.74 Bayesian posterior probability (“weak support”).

FIG. 32. Fifty-percent majority rule consensus of post-burn-in trees that results from undated Bayesian analysis of our total evidence dataset. Black dots at nodes indicate ≥0.95 Bayesian posterior probability (“strong support”); dark gray dots indicate 0.75–0.94 Bayesian posterior probability (“moderate support”); light gray dots indicate 0.50–0.74 Bayesian posterior probability (“weak support”).