English: 3D renderings of the holotype fossil of Irritator challengeri (SMNS 58022) in right lateral view. (a) solid rendering of the skull with interpretative line drawing indicating gross anatomy; (b) transparent rendering of the skull with solid rendering of the cranial endocast and endosseous labyrinth. Note that the skull is inclined according to the ‘alert’ head pos-ture inferred by lateral semicircular canal horizontality (see text for details). Scale bar equals 100 mm. Abbreviations: aof, antorbital fenestra; ar, articular; bc, brain-case; cr, cranium; end, cranial endocast; exn, external naris; itf, infratemporal fenestra; j, jugal; l-, indicates left element; lab, endosseous labyrinth; mx, maxilla; n, nasal; or, orbit; pra, prearticular; r-, indicates right element; s, stapes; sa, surangular.