Text-fig. 4. Metacheiromys marshii, AMNH 131777, basicranial isosurface from CT scans in oblique posteroventral view: left petrosal in blue and small piece of left entotympanic in red. The white arrow on the left petrosal passes through a canal traversed by the tympanic nerve. Abbreviations: abX – foramen for auricular branch of vagus nerve, aptt – anteroventral process of tegmen tympani, as – alisphenoid, bo – basioccipital, bs – basisphenoid, ctp – caudal tympanic process, eam – squamosal roof

Text-fig. 4. Metacheiromys marshii, AMNH 131777, basicranial isosurface from CT scans in oblique posteroventral view: left petrosal in blue and small piece of left entotympanic in red. The white arrow on the left petrosal passes through a canal traversed by the tympanic nerve. Abbreviations: abX – foramen for auricular branch of vagus nerve, aptt – anteroventral process of tegmen tympani, as – alisphenoid, bo – basioccipital, bs – basisphenoid, ctp – caudal tympanic process, eam – squamosal roof of external acoustic meatus, ec – ectotympanic, en – entotympanic, eo – exoccipital, hf – hypoglossal foramen, ips – foramen for inferior petrosal sinus, ljf – lateral jugular foramen, me – mastoid exposure of petrosal, mjf – medial jugular foramen, mt – muscular tubercle, oc – occipital condyle, pcf – posterior carotid foramen, pp – paroccipital process of petrosal, pr – promontorium of petrosal, ptp – posttympanic process of squamosal, smf – stylomastoid foramen, sq – squamosal, stf – stapedial artery foramen, tca – tympanic canaliculus, th – tympanohyal.