English: Craniodental morphology of Gustafsonia cognita, g (a) left P3-M2 of cast of holotype TMM 40209-200 in occlusal view; (b) same in oblique lingual view; (c) digital three-dimensional reconstruction (see text) of holotype cranium in ventral view, showing locations of basicranial embayment (blue) for inferior petrosal sinuses; (d) left basicranial morphology, magnified from boxed area in (c) and indicating position of coronal section no. 832 figured in (f); (e) external ventral view of left basicranial region (cast of holotype; basioccipital embayment is invisible, and its approximate medial extent is marked by dashed line); (f) coronal section no. 832 from Digital Morphology Library (see text) showing cross-section through the left auditory region of holotype (ventral to top; lateral to right). Panels (c,d,f) produced with permission from the University of Texas HRXCT Facility. Abbreviations: as, alisphenoid; be, basioccipital embayment for inferior petrosal sinus; bs, basisphenoid; cf, condyloid foramen; cica, canal (dotted line) for anterior loop of internal carotid artery; dbo, dorsal lip of basioccipital; er, epitympanic recess; fc, fenestra cochlea; fs, fossa for stapedius muscle; Gf, Glaserian fissure; mlf, middle lacerate foramen; mp, mastoid process; mt, mastoid tubercle; oc, occipital condyle; pgf, postglenoid fossa; plf, posterior lacerate foramen; pr, petrosal promontorium; vbo, ventral floor of basioccipital.