Stenoplacosaurus n. gen.
Robert M. Sullivan and Liping Dong (2018)
Stenoplacosaurus mongoliensis, a new generic name for "Placosaurus" mongoliensis (Anguidae, Glyptosaurinae) from the Shara Murun Formation, Nei Mongol (Inner Mongolia), China.
in Lucas, S.G. and Sullivan, R.M., eds., 2018, Fossil Record 6. New Mexico Museum of Natural History and Science Bulletin 79: 691-694
The genus Stenoplacosaurus (n. gen.) is established for the holotype of "Placosaurus" mongoliensis. The holotype of Stenoplacosaurus mongoliensis, from the middle Eocene Shara Murun Formation (Sharamurunian age), is distinct from the European Placosaurus rugosus and P. estesi based, in part, onhaving slender unfused frontalsand fewer osteoderms covering the frontal bones. A nearly complete pair of frontals from the Rencun Member, Heti Formation (Sharamurunian), bears a near identical morphology and osteoderm distribution on the frontals, and is thus considered to be an exemplar of this species. Recent phylogenetic analyses have confirmed the distinct nature of the taxon Placosaurus rugosus. However, P. estesi is here retained in the genus Placosaurus, based on having concave frontal orbital borders and a W-shaped frontonasal suture, two characters that were misinterpreted in recent studies. The retention of P. estesi in the genus Placosaurus is consistent with its age and geographic proximity to the holotype, P. rugosus. Morphological differences between P. rugosus and P. estesi are considered specific and not generic.
Spencer G. Lucas, Emily D. Thorpe, David S. Berman, Larry F. Rinehart, Vincent L Santucci and Amy C. Henrici (2018)
Discovery of a tetrapod body fossil in the Lower Permian Yeso group, central New Mexico.
in Lucas, S.G. and Sullivan, R.M., eds., 2018, Fossil Record 6. New Mexico Museum of Natural History and Science Bulletin 79: 493-497.
The lower Permian Yeso Group records arid coastal plain, shallow marine and evaporitic deposition across much of central New Mexico during Leonardian time. Generally considered to have few fossils, recent study of Yeso Group strata has uncovered a diverse fossil record of marine microorganisms (mostly algae and foraminiferans), terrestrial plants and tetrapod footprints. We document the discovery of a tetrapod body fossil in the Yeso Groupâa partial skeleton of a varanopid eupelycosaur. The fossil consists of the natural molds of articulated bones in two pieces, part and counterpart, that were preserved in a sandstone bed of the lower part of the Arroyo de Alamillo Formation in the southern Manzano Mountains. The fossil-bearing sandstone is interpreted as an eolian sheet sand. The casts preserve part of the pelvis(?), 18 caudal vertebral centra, both femora, tibia-fibulae, and most of the pedes, largely in close articulation, of a single individual. The skeleton is of a relatively small (femur length = 62 mm, total length of the preserved cast from the pelvis to tip of the incomplete tail = 325 mm) and gracile eupelycosaur most similar to Varanops. In New Mexico, various early Permian eupelycosaurs are known from the older strata of the Bursum Formation, Abo Formation, and Cutler Group, so this discovery extends the eupelycosaur fossil record in the state into younger early Permian strata. It also indicates that a substantial community must have been present on the arid coastal plain during deposition of the Arroyo de Alamillo Formation, as the varanopid is a generally large, early Permian predator that likely fed on smaller vertebrates and arthropods. Furthermore, this discovery indicates the potential for additional discoveries of tetrapod body fossils in Yeso Group strata.