Three-dimensional reconstruction of the skull of Helminthophis flavoterminatus (AMNH R 59407), based on HRXCT data. A. Transversal view; B. Frontal view; C. Sagittal view. Scale bar: 1 mm. Anatomical abbreviations: a, angular; an, acoustic nerve foramen; bo, basioccipital; cb, compound bone; cbp, compound bone prearticular component; cbs, compound bone surangular component; ci, conchal invagination; co, coronoid; cv, cavum vestibuli; d, dentary; dp, descensus parietalis; ec, ectopterygoid; f, frontal; fl, frontal laterally descending flange; fo, foramen; fpb, facial nerve palatine branch foramen; fs, frontal subolfactory process; fv, fenestra vomeronasalis; m, maxilla; Mc, Meckel’s canal; n, nasal; nl, nasal lateral flange; ns, medial nasal septum; oc, occipital condyle; on, optic nerve foramen; ooc, otico–occipital (fused prootic + opisthotic + exoccipital); p, parietal; pa, palatine; pbc, parabasal (Vidian) canal; pbs, parabasisphenoid; pe, postorbital element; pf, prefrontal; pg, pterygoid; pm, premaxilla; pvs, posterior vertical semicircular canal; q, quadrate; rstm, recessus scalae tympani medial aperture; s, stapes; sm, septomaxilla; sml, septomaxilla lateral flange; trc, trigeminofacialis chamber; v, vomer; vc, vomeronasal cupola; vn, vomeronasal nerve passage.