Notoryctemorphia Kirsch 1977

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 : 208

Notoryctemorphia Kirsch 1977

CONTENTS: Notoryctes (fig. 36).

STEM AGE: 45.7 Mya (95% HPD: 42.3–49.2 Mya).

CROWN AGE: N/A.

UNAMBIGUOUS CRANIODENTAL AUTAPOMORPHIES: Nasals truncated anterior to lacrimals (char. 3: 0→1; ci = 0.333); entire orbital mosaic fused (char. 12: 0→2; ci = 1.000); foramen rotundum ventral to sphenorbital fissure (char. 17: 0→2; ci = 0.286); median suture between left and right frontals at least partially fused in subadults (char. 24: 0→1; ci = 0.143); frontal and squamosal in contact on lateral aspect of braincase (char. 26: 0→1; ci = 0.071); auditory bulla large, contacting rostral process of petrosal, or very large, extending posteriorly across the petrosal to contact the exoccipital (char. 55: 1→2 or 1→3; ci = 0.300); ectotympanic concealed from lateral view within bulla (char. 57: 0→1; ci = 0.500); anterior limb of ectotympanic attached firmly to postglenoid process of squamosal (char. 59: 1→2; ci = 0.214); anterior process of malleus entirely absent (char. 64: 0→2; ci = 0.500); rostral and caudal tympanic processes of petrosal seamlessly fused, forming a petrosal plate (char. 68: 0→2; ci = 0.154); 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); external auditory meatus ventral to postglenoid fossa (char. 78: 1→2; ci = 1.000); facial nerve exits middle ear via a stylomastoid foramen formed by the ectotympanic, posttympanic process of the squamosal, and pars canalicularis of the petrosal (char. 79: 0→4; ci = 0.625); one hypoglossal foramen present (char. 92: 0→1; ci = 0.500); masseteric fossa perforated by a distinct masseteric foramen (char. 99: 0→1; ci = 0.333); first upper premolar (P1) absent (char. 114: 0→1; ci = 0.200); P2 single-rooted and caniniform or vestigial and occlusally featureless (char. 118: 0→4: ci = 0.444); paracone lost entirely, only metacone present (char. 137: 1→2; ci = 0.400); and talonid greatly reduced or absent (char. 166: 0→1; ci = 0.500).

COMMENTS: Notoryctes (the only living representative of the family Notoryctidae and order Nortoryctemorphia ) is one of the morphologically most specialized known marsupials. This is reflected in our long list of unambiguous craniodental autapomorphies, which include a number of highly unusual or unique features within Marsupialia , among them: fusion of the entire orbital mosaic, the foramen rotundum positioned ventral (rather than lateral) to the sphenorbital fissure, concealment of the ectotympanic in lateral view by the auditory bulla (convergent with microbiotheriids), complete absence of the anterior process of the malleus, position of the external auditory meatus ventral (rather than posterior) to the glenoid fossa, presence of only a single hypoglossal foramen (convergent with Tarsipes ), total loss of the paracone, and extreme reduction of the talonid (convergent with † Yalkaparidon ; Archer et al., 1988, 2011; Asher and Sánchez-Villagra, 2005; Beck et al., 2014).

Our estimated time for the divergence of Notoryctemorphia from other agreodontians dates to the early or middle Eocene, corresponding to a major gap in the fossil record of Australian mammals. † Naraboryctes philcreaseri from early Miocene sites at Riversleigh World Heritage Area ( Archer et al., 2011; Beck et al., 2016) and a single upper molar of a probable notoryctemorphian from the late Oligocene Pwerte Marnte Marnte Local Fauna in the Northern Territory (NTM P2815-6; Murray and Megirian, 2006b; Beck et al., 2014: 151, 2016: 166) are the only known fossil members of the order. They have not been included in this study due to their incompleteness, but both are dentally markedly more plesiomorphic than Notoryctes ; most notably, their molars are not fully zalambdodont, as both retain a distinct paracone on their upper molars, and † Naraboryctes has an unreduced talonid basin on its lower molars ( Murray and Megirian, 2006b; Archer et al., 2011; Beck et al., 2016). Inevitably, our long list of notoryctemorphian synapomorphies will be whittled down as plesiomorphic fossil taxa are added to future analyses, with the probable result that some of these traits may prove to be autapomorphies of Notoryctes .