Ilariidae Tedford and Woodburne, 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 : 232

† Ilariidae Tedford and Woodburne, 1987

CONTENTS: † Ilaria .

STEM AGE: 30.5 Mya (95% HPD: 27.3–34.1 Mya).

CROWN AGE: N/A.

UNAMBIGUOUS CRANIODENTAL AUTAPOMORPHIES: Mandibular symphysis fused (char. 97: 0→1; ci = 0.333); masseteric fossa imperforate (char. 99: 1→0; ci = 0.333); and metacone much larger than paracone (char. 137: 1→2; ci = 0.400).

COMMENTS: This enigmatic family is currently known from three named species. † Ilaria illumidens and † I. lawsoni are calf-sized taxa (~ 150 kg; Beck et al., 2020: supplementary information) from the late Oligocene Pinpa Local Fauna of the Namba Formation, South Australia ( Tedford and Woodburne, 1987), whereas † Kuterintja ngama is a much smaller taxon (~ 16 kg; Beck et al., 2020: supplementary information) from sites in South Australia and Queensland ( Pledge, 1987a; Myers and Archer, 1997) that are also late Oligocene ( Black et al., 2013; Woodhead et al., 2014; Arena et al., 2015). Additionally, an unnamed ilariid, intermediate in size between † Ilaria and † Kuterintja , is known from the late Oligocene Pwerte Marnte Marnte Fauna of the Northern Territory ( Murray and Megirian, 2006b). The apparent absence of representatives of this morphologically distinctive family from sites younger than the late Oligocene suggests that ilariids probably went extinct around the Oligocene-Miocene boundary ( Black et al., 2012b).

Only † Ilaria has been included as a terminal here, because it is the sole ilariid known from cranial material ( Tedford and Woodburne, 1987); other ilariids are known primarily from fragmentary dental material. Ilariids have been universally accepted to be vombatiforms since their original description, but their position within Vombatiformes is controversial ( Marshall et al., 1990; Murray, 1998; Archer et al., 1999; Black et al., 2012b) and has varied among phylogenetic analyses ( Munson, 1992; Gillespie, 2007; Black, 2008; Black et al., 2012a; Brewer et al., 2015; Gillespie et al., 2016; Beck et al., 2020). Our undated total-evidence analysis (fig. 32) places † Ilaria as sister to † Wynyardiidae († Muramura + † Namilamadeta ), a result also reported by Black (2008), Black et al. (2012a), and Gillespie et al. (2016). However, our dated total-evidence analysis ( fig. 33) places † Ilaria in a trichotomy at the base of Vombatomorphia with † Diprotodontidae and Vombatidae + † Namilamadeta + † Muramura († Wynyardiidae is paraphyletic in this analysis). The morphological analysis of Beck et al. (2020), meanwhile, placed ilariids as sister to all other vombatomorphians.

The lower molars of ilariids are distinctive ( Pledge, 1987a; Tedford and Woodburne, 1987; Myers and Archer, 1997; Murray and Megirian, 2006b). An apparently neomorphic cuspid is present between the protoconid and metaconid, and another is present between the hypoconid and entoconid. We did not score presence of the anterior neomorphic cuspid due to difficulties in defining clearly discrete states (particularly when taking into account the complex trigonid morphology seen in pseudocheirids; Archer, 1984c), but we did score presence/absence and morphology of the posterior neomorphic cuspid, which we refer to as an entostylid (see char. 174). However, presence of a cusplike (versus crestlike) entostylid was not identified as an unambiguous autapomorphy of † Ilariidae in our analyses, presumably because similar structures are also present in † Namilamadeta and phascolarctids.