New Mexico Geological Society Annual Spring Meeting — Abstracts

A student at New Mexico Tech recently discovered a new Middle Paleocene, Nacimiento Formation (Torrejonian) fossil locality north of Bloomfield, New Mexico and salvaged an exposed incomplete fossil mandible with m₁-m₃. The cusp morphology and measurements of the teeth are within the range of variation of Litaletes disjunctus Simpson; this is the first occurrence of this interesting condylarth in the Middle Paleocene (Torrejonian) of the San Juan Basin. The paraconid is the tallest cusp; metaconid is small, poorly separated and internal. The protoconid is well developed. The hypoconid is large and slightly labial; entoconid present and joins the hypoconulid in m₃. Talonid basins deepen lingually. The precingulid is low and anteriorly complete; paracristid arcuate, postcristid linear; trigonid basin constricted but deep. The cristid oblique is wen developed.

Simpson described Litaletes disjunetus in 1935 from Gidley Quarry, Crazy Mountain Field, Montana. He noted its similarity to Ellipsodon aquilonius. Gazin described Ellipsodon shepherdi, E.? sternbergi and Jepsenia mantiensis from the North Horn Formation, Dragon Canyon, Emery County, Utah, and noted the similarity of J. mantiensis and L. disjunetus. In 1978, Van Valen suggested that Ellipsodon shepherdi and Jepsenia mantiensis are synonyms for new combination, Litaletes sternbergi. In 1980, Rigby described the Swain Quarry fauna and referred J. mantiensis to still another new combination, Litaletes mantiensis without explaining why or referencing Van Valen. It is likely that L. mantiensis of Rigby actually comprises at least two taxa, one of which is certainly L. sternbergi sensu Van Valen. Rigby also described Promioclaenus acolytus (Cope); at least two taxa are also contained therein, one of which is also Litaletes sternbergi of Van Valen, as well as Promioclaenus wilsoni of Van Valen. Finally, in 1976, Hartman describes Litaletes disjunetus from the Bench Formation of Wyoming. Litaletes sternbergi, EllipsodonI shepherdi, and Jepsenia mantlensis are synonyms, but they are synonyms of Litaletes disjunetus. L. disjunetus is thus widely known from the Torrejonian with occurrences in Montana, Utah, Wyoming and New Mexico; it is a useful Torrejonian index fossil.