1096


Journal of Paleontology


Figure 5. Nectridea indet. (TMM 43628-7): (1) photograph in dorsal profile; (2) illustration of Figure 5.1; (3) photograph in ventral profile; (4) illustration of Figure 5.3. cl, clavicle; j, jugal; ns, neural spine; p, parietal; pp, postparietal; ppf, postpterygoid fossa; psp, parasphenoid; pt, pterygoid; qj, quadratojugal; sq, squamosal; t, tabular. Scale bar=1 cm.


parietals and squamosals are incomplete (Fig. 5.1, 5.2). Of the three nectridean specimens, the sutural contacts can be most readily defined in this specimen and are comparable to both those of a referred specimen of Diplocaulus sp. from this locality (below) and to previously described immature speci- mens of the genus (Olson, 1951a). The postparietals are trans- versely elongate rectangles, as in nectrideans with broader skulls. The quadratojugal has both dorsal and ventral exposures in association with the dorsoventral compression of the skull in diplocaulines. The tabular horns are incompletely developed but extend posteriorly and slightly laterally. The posterior margin of the skull forms a smooth concave curve, typical of diplocaulines in comparison to the squared-off margin of other nectrideans such as Scincosaurus Fritsch, 1876 and Diceratosaurus Jaekel, 1903 (Bossy and Milner, 1998; Milner and Ruta, 2009). The


posterior portion of the palate is highly fragmentary but identi- fiable based on the presence of symmetrical, oval postpterygoid fossa. However, this specimen is the most difficult to further resolve because of the nature of a pair of clavicles that are pre- served in the palatal region (Fig. 5.3, 5.4). The clavicles are of identical shape and comparable ornamentation to those of Diplocaulus (Williston, 1909b), but they contact each other anteriorly before being divided posteriorly by a small anterior


Figure 4. Tetrapoda indet. and Diplocaulinae gen. indet. sp. indet., a juvenile diplocauline with an indeterminate tetrapod on the dorsal skull roof (TMM 43628-8): (1) close-up of the indeterminate tetrapod; (2) dorsal profile of the diplocauline; (3) ventral profile of the diplocauline. ang, angular; f, frontal; p, parietal; pp, postparietal; qj, quadratojugal; sp, splenial; sq, squamosal; sur, surangular; t, tabular. Scale bars=2.5mm (1); 1cm (2, 3).


process of the absent interclavicle in a similar fashion to that figured by Germain (2010, p. 38) for Scincosaurus; this rela- tionship is not seen in any diplocauline and among nectrideans, is known only in Scincosaurus and Diceratosaurus (Bossy and Milner, 1998). That this disparity from previously described diplocauline material could be an ontogenetic shift cannot be excluded; the pectoral girdle of diplocaulines has not been extensively described or figured in articulation beyond that of


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