Text-fig. 3. Metacheiromys marshi, USNM-P 452349, coronal sections from CT scans. a – section 590 of 2020 through the anteriormost tympanic cavity showing air spaces in the entotympanic and squamosal; b – section 898 of 2020 at level of the fenestra vestibuli showing the mastoid sinus. Abbreviations: bo – basioccipital, bs – basisphenoid, cp – crista parotica, ec – ectotympanic, en – entotympanic, es – epitympanic sinus of squamosal, fv – fenestra vestibuli, hyf – hypophyseal fossa, m – malleus,

Text-fig. 3. Metacheiromys marshi, USNM-P 452349, coronal sections from CT scans. a – section 590 of 2020 through the anteriormost tympanic cavity showing air spaces in the entotympanic and squamosal; b – section 898 of 2020 at level of the fenestra vestibuli showing the mastoid sinus. Abbreviations: bo – basioccipital, bs – basisphenoid, cp – crista parotica, ec – ectotympanic, en – entotympanic, es – epitympanic sinus of squamosal, fv – fenestra vestibuli, hyf – hypophyseal fossa, m – malleus, ms – mastoid sinus, pr – promontorium, sq – squamosal, tc – tympanic cavity.