a–c, Comparison of occiputs of the cynodont Thrinaxodon liorhinus (based in part on University of California Museum of Paleontology (UCMP) 40466) (a), C. wahkarmoosuch (b) and Vintana sertichi (based on figure 1 of Krause et al.18) (c). Shaded bones in b and c emphasize sutural union of postparietal and paroccipital process. Skulls are not shown to scale. d–h, Brain endocasts. Cifelliodon endocast shown in left lateral (d) and posterior oblique (e) views. Skull of Vintana in lateral view shown externally (f) and with endocranial features exposed (g) (modified from figure 1 of Hoffmann et al.36 flipped for comparison). Skull of Hadrocodium (h) shown as a representative plesiomorphic mammaliaform (modified from figure 1 of Rowe et al.22; flipped for comparison). Numbers represent characters and character states described in the Supplementary Information. cb, cerebellar hemisphere; eo, exoccipital; f j, cast of jugular foramen within perilymphatic fossa; nc, region of neocortex; ob, olfactory bulb; p pr, paroccipital process; pf, paraflocculus cast; pp, postparietal; so, supraoccipital; II, III, IV, V1, exit for anterior cranial nerves near sphenorbital fissure; V3, V2, roots of mandibular (and maxillary?) branch of trigeminal nerve; IX, X, roots of glossopharyngeal and vagus nerves.