Myrmecobiidae Waterhouse 1841
Creators: name: Beck, Robin M. D.
name: Voss, Robert S.
name: Jansa, Sharon A.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Dasyuromorphia
Myrmecobiidae

description: Myrmecobiidae Waterhouse, 1841   CONTENTS: Myrmecobius (fig. 41).   
STEM AGE: 20.2 Mya (95% HPD: 14.4–25.3 Mya).  
CROWN AGE: N/A.  
UNAMBIGUOUS CRANIODENTAL AUTAPOMORPHIES: Masseteric process present and projecting ventrally below plane of molar alveoli (char. 6: 0→1; ci = 0.125); jugal terminates in a ventrally expanded ectoglenoid crest (char. 22: 0→1; ci = 0.167); glenoid process of alisphenoid absent (char. 23: 1→ 0; ci = 0.125); scars of M. temporalis origin on braincase not fused middorsally to form sagittal crest in adults (char. 27: 1→0; ci = 0.059); maxillopalatine fenestrae consistently absent (char. 36: 1→0; ci = 0.111); posterolateral palatal foramina present, with complete posterior margins (char. 40: 1→0; ci = 0.200); palate extends posterior to presphenoid-basisphenoid suture (char. 42: 0→1; ci = 1.000); pterygoids separated from presphenoid by palatine-basisphenoid contact (char. 46: 0→1; ci = 0.111); pterygoids long, extending posteriorly to sheath the ventral margin of the carotid canal (char. 47: 0→1; ci = 0.333); masseteric fossa perforated by a distinct masseteric foramen (char. 99: 0→1; ci = 0.333); angular process weakly or not inflected (char. 102: 0→1; ci = 0.250); premolariform second upper premolar (P2) distinctly taller than premolariform P3 (char. 119: 2→0; ci = 0.118); i2 alveolus like those of i1 and i3 (char. 149: 0→1; ci = 0.250); paraconid well developed, but paracristid indistinct or absent on m1 (char. 159: 0→2; ci = 0.400); paraconid well developed, but paracristid indistinct or absent on m2 and m3 (char. 161: 0→2; ci = 0.667); cristid obliqua absent or indistinct (char. 167: 0→1; ci = 0.500); hypoconid small and indistinct (char. 172: 0→1; ci = 0.333); and entocristid indistinct or absent (char. 176: 0→1; ci = 0.077).  
 COMMENTS: Kealy and Beck (2017: table 1) defined Myrmecobiidae as the most inclusive clade including Myrmecobius fasciatus, but excluding Dasyurus viverrinus and Thylacinus cynocephalus. Under this definition, our dated total-evidence analysis (fig. 33) indicates that the fossil dasyuromorphians † Barinya and † Mutpuracinus are myrmecobiids, as did the dated total-evidence analysis of Kealy and Beck (2017: fig.3). Given our estimate for the age of the split between the Myrmecobius lineage and Dasyuridae (median: 24.9 Mya; 95% HPD: 21.8–29.4 Mya) and those of other recent studies (e.g., Mitchell et al., 2014; Westerman et al., 2016; Kealy and Beck, 2017), we would expect stemmyrmecobiids in the fossil record from at least the early Miocene onward; the earliest of these would presumably have had a “typical,” unreduced dasyuromorphian dentition, in contrast to the secondarily simplified dentition of Myrmecobius. Thus, it is not implausible that † Barinya and † Mutpuracinus are indeed early myrmecobiids. However, the Myrmecobius + Barinya + Mutpuracinus clade receives only relatively weak support here (BPP = 0.67), and only one craniodental feature optimizes as an unambiguous synapomorphy, namely loss of the posterior cutting edge of P3 (char. 124: 1→2; ci = 0.667), which is clearly the case in † Barinya (Wroe, 1999), but which cannot be scored in † Mutpuracinus based on available material (Murray and Megirian, 2000; Murray and Megirian, 2006a). We consider the evidence that Barinya and Mutpuracinus are stem myrmecobiids to be equivocal pending further studies, so we here restrict Myrmecobiidae to Myrmecobius.   
 Myrmecobius is characterized by a long list of craniodental apomorphies not seen in other dasyuromorphians: many of these are dental, but there are also a large number of unusual cranial features (see also Archer, 1976b, 1984c; Archer and Kirsch, 1977; Friend, 1989; Cooper, 2000). At least some of these apomorphies are likely related to myrmecophagy, including several relating to simplification of the molars (reflecting little or no occlusion between the upper and lower dentition; Charles et al., 2013).
description: Published as part of Beck, Robin M. D., Voss, Robert S. & Jansa, Sharon A., 2022, Craniodental Morphology And Phylogeny Of Marsupials, pp. 1-353 in Bulletin of the American Museum of Natural History 2022 (457) on page 220, DOI: 10.1206/0003-0090.457.1.1, http://zenodo.org/record/6971356