Fig 1.
Geological map of the Los Colorados Formation, Ischigualasto-Villa Unión Basin, La Rioja, Argentina.
Star indicates the location where the specimens were collected. Modified from Baczko et al. 2014.
Fig 2.
Skulls of Riojasuchus tenuisceps in right lateral view.
(A) Holotype PVL 3827; (B) reconstruction based on both specimens; (C) Referred specimen PVL 3828. Abbreviations: An, angular; AOF, antorbital fenestra; Aofo, antorbital fossa; CN V, exit for cranial nerve V; De, dentary; EMF, external mandibular fenestra; EN, external nares; Fr, frontal; ITF, infratemporal fenestra; J, jugal; J.pb, protuberance of the jugal; J.vp, vertical process of the jugal; La, lacrimal; La.p, pocket on the lacrimal; Ls, laterosphenoid; Mx, maxilla; N, nasal; O, orbit; Op, opisthotic; Pa, parietal; Pfr, prefrontal; Pl, palatine; Pmx, premaxilla; Pmx,pp, palatal process of the premaxilla; Po, postorbital; Pof, postfrontal; Pp, paroccipital process; Pr, prootic; Q, quadrate; Qj, quadratojugal; Sa, surangular; Sa.sh, surangular shelf; Sq, squamosal; STF, supratemporal fenestra. Scale bar: 1cm.
Fig 3.
Holotype skull of Riojasuchus tenuisceps in dorsal and ventral view.
(A) dorsal view of PVL 3827; (B) ventral view of PVL 3827; (C) detail of possible palatine teeth. Lower halves as interpretative drawing. Abbreviations: AOF, antorbital fenestra; An, angular; Ar, articular; Bo, basioccipital; Bo.r, basioccipital recess; Bpt, basipterigoid process; Bs, basisphenoid; Bs.r, basisphenoid recess; Bt, basal tubera; Ch, choana; De, dentary; EN, external nares; Ept, ectopterygoid; Fr, frontal; Iptv, interpterygoid vacuity; ITF, infratemporal fenestra; J, jugal; J.pb, protuberance of the jugal; La, lacrimal; Mx, maxilla; N, nasal; O, orbit; Op, ophistotic; Pa, parietal; Pfr, prefrontal; Pl, palatine; Pl-Pt-f, palatine-pterygoid fenestra; Pl.r, palatine ridge; Pmx, premaxilla; Po, postorbital; Pof, postfrontal; Pra, prearticular; Pt, pterygoid; Q, quadrate; Q.f, quadrate foramen; Qj, quadratojugal; Sp, splenial; Sq, squamosal; STF, supratemporal fenestra; So, supraoccipital; Sor.f, Suborbital fenestra; V, vomer. Scale bar: 1cm.
Fig 4.
Details of dentition of Riojasuchus tenuisceps.
(A) lateral detail of denticles on distal margin of maxillary tooth (PVL 3828); (B) anterior view of first dentary tooth (PVL 3827) broken at its base; (C) medial view of posterior dentary tooth (PVL 3828) with denticles on distal margin; (D) 3D reconstruction of the skull of PVL 3827 indicating selected slices; (E-F) selected slices of PVL 3827; (G) detail of slide E indicating a maxillary replacement tooth (Mrt) erupting; (H) detail of slide F pointing out a dentary replancement tooth (Drt); *1 and *2 indicate the position of each replacement tooth on the skull. Arrowheads point at denticles. Abbreviations: Al, alveoli; Aofe, antorbital fenestra; Aofo, antorbital fossa; De, dentary, Drt, dentary replacement tooth; Fr, frontal; N, nasal; Mrt, maxillary replacement tooth; Mx, maxilla; Pa, parietal; Pl, palatine; Pmx, premaxilla; Pp, paroccipital process; Pr, prootic; Pt, pterygoid; Q, quadrate; So, supraoccipital. Scale bar: 2mm.
Fig 5.
Holotype skull of Riojasuchus tenuisceps PVL 3827 in occipital view.
Left half as interpretative drawing. Abbreviations: Ar, articular; Ar,rp, retroarticular process of the articular; Bo, basioccipital; Bpt, basipterygoid process; Bt, basal tubera; CN XII?, possible exit for cranial nerve XII; Eo, exoccipital; FM, foramen magnum; Op, opisthotic; Pa, parietal; Pp, paroccipital process; Pt, pterygoid; PTF, posttemporal fenestra; Q, quadrate; Q.f, quadrate foramen; Q.r, quadrate ridge; Qj, quadratojugal; Sq, squamosal; So, supraoccipital. Scale bar: 1cm.
Fig 6.
Left hemimandible of holotype of Riojasuchus tenuisceps PVL 3827.
(A) lateral view; (B) medial view. With interpretative drawings. Abbreviations: An, angular; Ar, articular; Ar.rp, retroarticular process of the articular; De, dentary; EMF, external mandibular fenestra; Gl, glenoid fossa; IMF, internal mandibular fenestra; Pra, prearticular; Sa, surangular; Sa.f, surangular foramen; Sa.sh, surangular shelf; Sp, splenial. Scale bar: 1cm.
Fig 7.
Digital endocast of the braincase of Riojasuchus tenuisceps PVL 3827.
(A) lateral, (B) dorsal, and (C) ventral view. Abbreviations: Ceh, cerebral hemispheres; CN V, cranial nerve V (trigeminal); Dlvs, dorsal longitudinal venous sinus; Hy, hypophysis; Inc, internal carotid arteries; Olf, olfactory tracts. Scale bar: 1cm.
Table 1.
List of comparative material.
Table 2.
Measurements of the skulls of PVL 3827 and 3828 (in cm).