Fig 1.
Geographic location of Cabeza Blanca locality.
Table 1.
Specimens examined for comparative purposes.
Table 2.
Cranial measurements of MPEF PV 695.
Scheme of measurements provided in S1 Fig.
Table 3.
Dental measurements of MPEF PV 695.
MD, mesiodistal diameter; EL, ectoloph length; LD, labiolingual diameter; PL, protoloph length; MDL, mesiodistal diameter measured along the lingual edge in occlusal view (Not considered by Madden [1990, unpublished PhD dissertation]); LDP, labiolingual diameter measured posteriorly, at the distal edge in occlusal view (Not considered by Madden [1990]); LCF, length of central fossette; LPCF, length of labial projection of central fossette. Scheme of measurements provided in S1 Fig.
Fig 2.
3D reconstruction of the skull of R. equinus (MPEF-PV 695).
(A) Lateral view. (B) Dorsal view. (C) Ventral view. Anatomical abbreviations: ab, auditory bulla; as, alisphenoid; bo, basioccipital; bs, basisphenoid; cf, condylar foramen; eam, external auditory meatus; ef, ethmoidal foramen; fm, foramen magnum; fo, foramen ovale; fro, frontal; ftr, foramina of temporal region; gf, glenoid fossa; if, incisive foramen; iof, infraorbital foramen; jf, jugular foramen; ju, jugal; mc, meatal crest; mpaf, major palatine foramen; mx, maxilla; na, nasal; nc, nuchal crest; oc, occipital; occ, occipital condyle; os, orbitosphenoid; pa, parietal; pal, palatine; palc, palatine crest; pf, piriform fenestra; pgf, postglenoid foramen; pgp, postglenoid process; pmx, premaxilla; pocp, paraoccipital process; pop, postorbital process; prgp, preglenoid process; ptc, pterygoid crest; sc, sagittal crest; scf, scaphoid fossa; smf, suprameatal foramen; sphr, sphenoidal rostrum; sq, squamosal; styf, stylomastoid foramen; suf, supraorbital foramen; ty, tympanic. Scale bar equals 2 cm.
Fig 3.
Palate and upper dentition of R. equinus (MPEF-PV 695).
Scale bar equals 2 cm.
Fig 4.
3D reconstruction of R. equinus (MPEF PV 695) and detail of the orbitotemporal region.
(A) Skull oriented to show foramina on the posterior orbital wall. (B) Skull oriented to show the sphenopalatine foramen and caudal palatine foramen. Maxilla in B rendered partially semitransparent to show the palatine canal. Anatomical abbreviations: as, alisphenoid; cpaf, caudal palatine foramen; eam, external auditory meatus; ef, ethmoidal foramen; es, epitympanic sinus; fro, frontal; iof, infraorbital foramen; ju, jugal; mc, meatal crest; mx, maxilla; na, nasal; oc, occipital; of, optic foramen; os, orbitosphenoid; otc, orbitotemporal canal; pac, palatine canal; pmx, premaxilla; pop, postorbital process; smf, suprameatal foramen; sof, sphenorbital fissure; spf, sphenopalatine foramen; sq, squamosal. Scale bar equals 2 cm.
Fig 5.
Hypothetical reconstruction of tensor veli palatini muscle and tendon in R. equinus (MPEF PV 695).
Anatomical abbreviations: ab, auditory bulla; as, alisphenoid; pal, palatine; palap, palatine aponeurosis; palc, palatine crest; pt, pterygoid; ptc, pterygoid crest; scf, scaphoid fossa; ttvp, tendon of tensor veli palatini muscle; tvp, tensor veli palatini muscle. Scale bar equals 2 cm.
Fig 6.
Posterior basicranial region of R. equinus (MPEF PV 695) and Nesodon imbricatus (FMNH P13105).
(A) 3D reconstruction of R. equinus. (B) Illustration of N. imbricatus taken and adapted from Patterson [24]. Numbers in parenthesis indicate same structures in A and B. Anatomical abbreviations: ab, auditory bulla; cf, condylar foramen; ecty, exit for chorda tympani nerve; et, eustachian tube; fo?, foramen ovale?; mc, meatal crest; occ, occipital condyle; pf?, piriform fenestra?; pgf, postglenoid foramen; pocp, paraoccipital process; sof, sphenorbital fissure; stypr?, styliform process?; tyhr, tympanohial recess. Not to scale.
Fig 7.
Tympanic cavity and paratympanic spaces of R. equinus (MPEF PV 695).
(A) CT slice at the level of tympanic bullae. (B) Left tympanic bulla transversally sectioned to appreciate internal morphology. (C) Squamosal + left tympanic bulla parasagittally sectioned to appreciate internal morphology of tympanic cavity and epitympanic sinus. Schemas on the left indicate orientation and cut planes. Striped areas represent cut surfaces. Dotted line in C shows the connection between tympanic cavity and epitympanic sinus via the foramen pneumaticum. Anatomical abbreviations: bo, basioccipital; eepe, endocranial exposure of petrosal; es, epitympanic sinus; iab, interior of auditory bulla; iaotm, internal aperture of the ossified tubular meatus; otg, orbitotemporal groove; pa, parietal; pgc, postglenoid canal; pr, promontory of petrosal; ptyc, paratympanic cavity; sq, squamosal. Scale bar equals 2 cm.
Fig 8.
Axial CT slice of R. equinus (MPEF PV 695) at level of the jugular foramen.
Anatomical abbreviations: bs, basisphenoid; eam, external auditory meatus; ica, internal carotid artery; jf, jugular foramen; mc, meatal crest; pa, parietal; pet, petrosal; pocp, paraoccipital process; smf, suprameatal foramen; sq, squamosal; ts, temporal sinus; tyc, tympanic cavity. Scale bar equals 1 cm.
Fig 9.
3D reconstruction of posterior skull of R. equinus (MPEF PV 695).
(A) Occipital view. (B) Posterolateral view with some vascular elements reconstructed. (C) Posterolateral view with some vascular elements reconstructed (semitransparent rendered). Arteries reconstructed in red and veins (and venous sinuses) in blue. Anatomical abbreviations: adm, arteria diploëtica magna; cev, capsuloparietal emissary vein; eam, external auditory meatus; ejv, external jugular vein; es, epitympanic sinus; fm, foramen magnum; iacf, internal aperture of condylar foramen; ijv, internal jugular vein; mc, meatal crest; mf, mastoid foramen; nc, nuchal crest; oc, occipital; occ, occipital condyle; oepet, occipital exposure of petrosal; oev, occipital emissary vein; ota, orbitotemporal artery; otv, orbitotemporal vein; pocp, paraoccipital process; ptf, posttemporal foramen; sc, sagittal crest; smf, suprameatal foramen; smv, suprameatal vein; sq, squamosal; ss, sigmoid sinus; stya, stylomastoid artery; styf, stylomastoid foramen; ts, temporal sinus; tv, temporal vessels; ty, tympanic; zc, zygomatic crest. Scale bar equals 2 cm.
Fig 10.
3D reconstruction of left petrosal of R. equinus (MPEF PV 695).
(A) Endocranial view. (B) Tympanic view. ICA partially reconstructed and hypothetical course of proximal stapedial artery depicted. Anatomical abbreviations: apcp, anteromedial process of crista petrosa; cp, crista petrosa; ew, epitympanic wing; fai, foramen acusticum inferius; fas, foramen acusticum superius; fc, fenestra cochleae; fv; fenestra vestibuli; ica, internal carotid artery; pc, prefacial commissure; pr, promontory of petrosal; saf, subarcuate fossa; sf, stapedial fossa; sff, secondary facial foramen; sta, stapedial artery course; tc, transverse crest. Scale bar equals 0.5 cm.
Fig 11.
Parasagitally sectioned 3D reconstruction of posterior skull of R. equinus (MPEF PV 695).
Internal surface of the braincase wall and some reconstructed vascular elements. Arteries reconstructed in red and veins (and venous sinuses) in blue. Anatomical abbreviations: adm?, arteria diploëtica magna?; cp, crista petrosa; fm, foramen magnum; iacf, internal aperture of condylar foramen; ijv, internal jugular vein; ips, inferior petrosal sinus; nc, nuchal crest; ota, orbitotemporal artery; otv, orbitotemporal vein; pet, petrosal; sof, sphenorbital fissure; ss?, sigmoid sinus?; ts, temporal sinus. Scale bar equals 2 cm.