Chelus, Dumeril, 1806

Cadena, EA & Jaramillo, CA, 2015, The first fossil skull of Chelus (Pleurodira: Chelidae, Matamata turtle) from the early Miocene of Colombia, Palaeontologia Electronica 24 (1), pp. 1-10 : 3

Genus CHELUS Dumeril, 1806

Included species. Chelus fimbriata Schneider, 1783 (extant, see Figure 2.1 -6), Chelus colombiana Wood, 1976 (sensu Cadena et al., 2008) (fossil), Chelus lewisi Wood, 1976 (fossil).

Revised diagnosis. Combined from Gaffney (1977) and Cadena et al. (2008). Chelus differs from all other chelid turtles by: (1) absence of nasal bones; (2) broad exposure of the prefrontals dorsally along the apertura narium; (3) anterior extension of the pterygoid into the apertura narium interna, often separating the vomer from the palatines; (4) extreme flattening of the dorsal skull, particularly in the center; (5) extreme lateral projection of the cavum tympani; (6) medial process of jugal and postorbital lying entirely on dorsal surface of skull; (7) maxilla very reduced in exposure on triturating surface, so that palatine bears lingual ridge; (8) basisphenoid with a bone tissue pattern extremely acicular tapering anteriorly; (9) dorsal surface of the parietals and frontals very rugose, with very deep sulci for scutes; (10) costovertebral tunnel of the carapace; (11) dorsal surface of the carapace ornamented with three prominently raised, longitudinal ridges, one bearing five knobs and extending along the midline of carapace; (12) scar on ventral surface for contact of inguinal buttress restricted to costal 4.

Figures

FIGURE 2. Skulls of Chelus fimbriata SM 37178 and Chelus sp. UNT-STRI-dbid 38473. Photographs and interpretative drawings. Chelus fimbriata SM 37178. 1-2, dorsal view; 3-4, ventral view; 5-6, posterior view. Chelus sp. MUN- STRI-dbid 38473 fossil from Castilletes Formation, Colombia. 7-8, dorsal view; 9-10, ventral view; 11-12, right lateral view; 13-14, posterior view. Abbreviations: bo, basioccipital; bs, basisphenoid; ex, exoccipital; fjp, foramen jugulare posterius; fm, foramen magnum; fn, foramen nervi hypoglossi, fp, fenestra postotica; fpcci, foramen posterior canalis caroticus cerebralis; fpp, foramen palatinum posterior; fr, frontal; fst, foramen stapedio temporalis; fts, fossa temporalis superior; ju, jugal; mx, maxilla; op, opisthotic; pa, parietal; pf, prefrontal; pl, palatine; pm, premaxilla; po, postorbital; pr, prootic; pt, pterygoid; qu, quadrate; so, supraoccipital; sq, squamosal; vo, vomer. Dotted line in 2 indicates sulci of skull scutes. Light grey areas in 8 indicate preservation of the dorsalmost surface of the bones. Scale bar applies for all figures.