FIG. 9. Thylacosmilus atrox, paratype, FMNH P14344, in A, oblique ventral and B, lateroventral views, with C, general key. Note that in A the detached bulla is in its original position. Abbreviations: AL, alisphenoid; bjs, basijugular sulcus; BO, basioccipital; BS, basisphenoid; cc, carotid canal; cod, occipital condyle; eam, external acoustic meatus;?EC,?ectotympanic; ewal, alisphenoid epitympanic wing; ewsq, squamosal epitympanic wing; EX, exoccipital; ffc, fossula fenestrae cochleae; fmg, foramen magnum; fo, foramen ovale; for, foramen rotundum; FR, frontal; fv, fenestra vestibuli; hfc, caudal hypoglossal foramen; hfr, rostral hypoglossal foramen; ips, inferior petrosal sinus; lps, lateral paratympanic space (= epitympanic sinus); PE, petrosal; pf, piriform fenestra; pgc, postglenoid canal;?sat,?sulcus for the auditory tube; sfn, septum for facial nerve; sjf, secondary jugular foramen; sof, sphenoorbital fissure; SQ, squamosal. Dashed line on left bulla marks suture track, the accuracy of which is undetermined. Asterisk (*) indicates unprepared area, within which the primary jugular foramen is located. The canal conducting the internal jugular and cranial nerves through the left bulla to the secondary jugular foramen on the latter's outer wall can be seen in B (broken during removal of right bulla, no longer identifiable on basicranium). Crosshatching indicates damage due to erosion or bullar removal. Arrow indicates the direction to or the position of features hidden by other structures.