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Journal of Paleontology
mid-region of the multiple-tooth-row area each have the typical moradisaurine conical shape. The captorhinids from the Arroyo Formation, Captorhinus and Labidosaurus (Olson, 1989), have up to four rows of somewhat randomly arranged teeth and one row, respectively; both are found in the Vale Formation in addition to Captorhinikos Olson, 1954c (Olson and Mead, 1982). An indeterminate moradisaurine tooth plate was descri- bed from the Vale Formation by Modesto et al. (2016), but that specimen possesses eight tooth rows and is evidently distinct from TMM 43628-12. The presence of five tooth rows on the maxilla is shared with Rothianiscus Olson, 1965, Gansurhinus Reisz et al., 2011, and Captorhinikos. There is no evidence of the slight cusp and recurvature seen in Gansurhinus, which is known from middle Permian deposits (Reisz et al., 2011). Rothianiscus is said to have up to seven tooth rows on the dentary (Olson, 1965). The maxillary teeth do not appear to be radiating insofar as the rows remain equally spaced throughout their length in the larger fragment, contrary to those of Cap- torhinikos valensis (see Modesto et al., 2014). The material is tentatively assigned to Captorhinikos
chozaensis because the taxon is known to occur in the same geographic region and because it does not display any differences from previously described material (Olson, 1954c; Vaugh, 1958). It should be noted that although Vaughn (1958) did not figure any of the specimens that he referred to this taxon, photographs of Vaughn’s specimen (USNM 21275) are publicly available on the Smithsonian Institution’s website.
Remarks.—The study of Captorhinikos valensis and broader phylogenetic analysis of captorhinids by Modesto et al. (2014) recovered C. chozaensis as the sister taxon to a clade containing Labidosaurus hamatus Cope, 1895 and the Moradisaurinae and suggested that it could warrant placement in a new genus. Because we have not reappraised the type or previously referred material of C. chozaensis and because the referral of the Mud Hill specimens is more tentative given the disparity in strati- graphic occurrence, we utilize the traditional taxonomic stand- ing sensu Olson (1954c).
Order Diadectomorpha Watson, 1917 Family Diadectidae Cope, 1880 Genus cf. Diadectes Cope, 1878
Type species.—Diadectes sideropelicus Cope, 1878 from the Admiral Formation, Texas, by original designation.
cf. Diadectes sp. indet. Figures. 9, S3–S5
Description.—The vast majority of the well-preserved diadectid is postcranial material, mostly vertebrae, with limb and girdle elements also being represented. An extremely fragmentary parabasisphenoid is also present. Because most diadectid diag- noses are based solely on cranial material, resolution for dis- articulated remains is difficult. Most of this material was collected from the D1 site (TMM 43628-4). A large portion of the material pertains to isolated thoracic and caudal centra that are characterized by markedly amphicoelous morphology and the lack of fusion to the neural arches (Fig. S3.1); at least 65
Figure 9. cf. Diadectes sp. indet., astragalus and partial tarsal bone (TMM 43628-5) from the D2 site: (1) ventral profile; (2) posterolateral profile; (3) anterior profile; (4) medial profile. Arrows point distally. Scale bar=5 cm.
centra have been collected from Mud Hill. The centra are slightly wider than they are long and with concave ventrolateral surfaces that meet at a shallow ventral midline ridge, differing from the centra of coeval synapsids (e.g., Dimetrodon), which are narrower and with a sharp ridge. The haemal arches are mostly lost. Neural arches are rare and fragmentary, which is again an indication of immaturity. A pair of articulated neural arches (TMM 43628-6) with the characteristic ‘swollen’ mor- phology was collected from the D3 site (Fig. S3.2). A large number of fragmentary ribs are also present. The appendicular material of TMM 43628-4 comprises three humeri (Fig. S4), a femur, a fibula, an ulna, and a radius. Extremely fragmentary limb material is also present. The limbs are characterized by unfinished bone at the ends, indicative of relative immaturity. A significant number of isolated phalanges, elements pertaining to the carpus and tarsus, and a complete left astragalus with a partial, articulated calcaneum are present (Fig. 9); some of these were collected from the D2 site (catalogued as TMM 43628-5). Association between any of these elements is unknown. Pec- toral material is represented by a dorsal fragment of a scapula- coracoid with a partial cleithrum (Fig. S5.1) and a partial clavicular stem. Pelvic material is represented by an ilium, a pubis, and an ischium (Fig. S5.2–S5.4); all three are of an appropriate size to pertain to a single individual, but they display a range of preservation and cannot be confidently fit together. At least two individuals were present based on the humeri count, but an association with more diagnostic cranial material (listed below) is unclear. The material cannot be confidently referred to Diadectes in the absence of preserved autapomorphies, but the taxon is abundant in the early Permian of North America and is confidently documented at the site (see below).
Diadectes Cope, 1878 Diadectes sp. indet. Figure 10
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