1098


Subclass Lepospondyli Zittel, 1888 Order Microsauria Dawson, 1863 Microsauria indet.


Description.—Several poorly-preserved ‘microsaurian’ verteb- rae are preserved within cylindrical segments of matrix, some- what reminiscent of burrow-like structures. However, ‘microsaurs’ are highly conserved in their vertebral morphol- ogy, and the exposures are limited to different cross-sectional profiles, preventing further resolution of these specimens. Additionally, most early Permian ‘microsaurs’ are recovered within Recumbirostra, which is identified as having a number of synapomorphies for fossorial behavior, so the occurrence within a putative burrow is also uninformative.


Clade Recumbirostra Anderson, 2007


Family Hapsidopareiontidae Carroll and Gaskill, 1978 Hapsidopareiontidae gen. indet. sp. indet. Figure 7


Description.—Recumbirostrans, a fossorially-adapted clade of tetrapods, are represented by a complete skull with articulated mandible (TMM 43628-10) measuring 16.3mm from the pre- maxilla to the postparietal that was collected from the D3 site. The specimen is slightly compressed dorsoventrally on the left


Journal of Paleontology


side, resulting in a slightly exaggerated width. In dorsal profile (Fig. 7.1, 7.2), the skull forms an equilateral triangle, with subequal width and length, similar to brachystelechids, panty- lids, some ostodolepids, and microbrachomorphs. In lateral profile (Fig. 7.4, 7.5), the skull is nearly entirely flat, with the tip of the snout oriented vertically in a fashion reminiscent of gymnarthrids, pantylids, and hapsidopareiontids. The posterior skull margin extends slightly posteromedially, forming an inverted triangle relative to the main skull roof. The dorsal exposures of the nares and the orbits are limited. The maxillary tooth count, estimated on the left side, is ~19–21. Sutural pat- terns of the skull roof are difficult to confidently elucidate, particularly on the posterior skull table and on the left side. A noteworthy observation is that the specimen appears to have a large temporal emargination of comparable size and relationship to that of hapsidopareiontids, being open ventrally; framed anteriorly by a reduced postorbital and a posteriorly truncated jugal with a rounded posteroventral terminus; framed dorsally by some combination of the postfrontal, the postorbital, the supratemporal, and the tabular; and framed posteriorly by a tall, slender squamosal that meets a small quadratojugal ventrally. That this opening appears on both sides of the skull suggests that it is not a taphonomic artifact and thus forms the basis for the taxonomic assignment. The emargination in other hapsidopar- eiontids (Daly, 1973; Bolt & Rieppel, 2009) differs from that of most other emarginated recumbirostrans (e.g., ostodolepids) in its large size, which occupies most of the temporal region. This results from the greater reduction of the temporal elements that produces the narrow, vertically oriented squamosal; the poster- iorly truncated jugal with a ventral margin dipping below the level of the maxilla; and the reduced lateral exposure of the tabular (e.g., Carroll & Gaskill, 1978; Anderson et al., 2009); these features are also seen in this specimen. The emargination of Brachydectes Cope, 1868 is comparable in size (Pardo & Anderson, 2016) but is open posteriorly. The lacrimal is blocky and tapers anteriorly; it joins both the narial and orbital margins. Two perforations for the lacrimal duct are present on the right side. The frontals are narrowly excluded from the orbital mar- gins by the pre- and postfrontal and posteriorly; they feature two slender processes that incise into the postfrontal and the parietal and a prominent medial flange from the left element that incises into the right counterpart. The dorsal exposure of the pre- maxillae is minimal. Aspects of the palate and mandibles are mostly unidentifiable. Because of the poor preservation of the material, further taxonomic resolution is not possible. The spe- cimen likely represents a new taxon insofar as it is distinct from all known ‘microsaurs’ and given the current absence of any ‘microsaurs’ in the Vale Formation, but because of the poor preservation and the difficulty in characterizing many aspects of the specimen, we refrain from erecting a new taxon at present.


Clade Eureptilia Olson, 1947


Figure 7. Hapsidopareiontidae gen. indet. sp. indet. (TMM 43628-10): (1) photograph in dorsal profile; (2) illustration of Figure 7.1; (3) photograph in ventral profile; (4) photograph in right lateral profile; (5) photograph in left lateral profile; (6) illustration of Figure 7.5. ang, angular; art, articular; d, dentary; f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; p, parietal; pf, prefrontal; pmx, premaxilla; po, postorbital; pof, postfrontal; pp, postparietal; sq, squamosal; t, tabular. Scale bars=1 cm.


Family Captorhinidae Case, 1911 Captorhinidae gen. indet. sp. indet. Figures. 8.1–8.3, S2


Description.—Indeterminate captorhinid material comprises both postcranial material consisting of several thoracic vertebrae and a right humerus (TMM 43628-11, Fig. S2) and mandibular


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