FIG. 16 in Caudal Cranium Of Thylacosmilus Atrox (Mammalia, Metatheria, Sparassodonta), A South American Predaceous Sabertooth

FIG. 16. Borhyaena tuberata MPM-PV 3625 from Puesto Estancia La Costa, Santa Cruz, Argentina; Santa Cruz Formation; Santacrucian, Early Miocene. Ventral view of A, the caudal cranium, with B, key; and MACN-A 5922 (C). Abbreviations: AL, alisphenoid; bjs, basijugular sulcus; BO, basioccipital; BS, basisphenoid; cc, carotid canal; cod, occipital condyle; cs, carotid sulcus; eam, external acoustic meatus; ewal, alisphenoid epitympanic wing; EX, exoccipital; ffc, fossula fenestrae cochleae; gf, glenoid fossa; hfc, caudal hypoglossal foramen; hfr, rostral hypoglossal foramen; ips, inferior petrosal sinus; ji, jugular incisure; pcp, paracondylar process; PE, petrosal; pf, piriform fenestra; pgf, postglenoid foramen; ptp, posttympanic process; SQ, squamosal. Unusually, in this specimen the caudal aperture of the inferior petrosal sinus is completely ringed by basioccipital bone. More often, the aperture opens in the basicapsular fissure, between the petrosal and basioccipital, in advance of the jugular foramen. Because the roof of the tympanic cavity is incompletely prepared, actual boundaries of the piriform fenestra are unknown. Asterisk (*) indicates groove for medial contact of petrosal. Arrow indicates the direction to or the position of features hidden by other structures.