FIG. 15 in The Serrialis Bone, Interparietals, "X" Elements, Entotympanics, And The Composition Of The Notoungulate Caudal Cranium

FIG. 15. Cochilius volens AMNH-VP 29651, four virtual coronal sections, left side (rev.), arranged in rostral to caudal order (for approximate locations of sectioning planes, see fig. 14A). All to scale in D. A, section through rostralmost end of bulla. Note fracturing (br) on medial surface of squamosal, which mimics a true suture. Arrow, discontinuity on rostral lip of bulla thought to represent nearly obliterated ectotympano-entotympanic suture. B passes through external acoustic meatus (note incus in epitympanic sinus, out of position post mortem). Arrow identifies caudal end of same groove seen in A. Except for petroso-bullar suture, other discontinuities are fractures. Asterisk identifies the large longitudinal fracture, seen on dorsal aspect of skull and positioned