Some pelecypods and scaphopods from the lower Wolfcampian (Basal Permian) Laborcita Formation, Sacramento Mountains, New Mexico
Barry S. Kues
Fifteen pelecypod and two scaphopod species from the lowest Wolfcampian Laborcita Formation are described and illustrated. These represent the majority of pelecypods and all of the scaphopods observed in the formation; neither group has been studied previously. Two new species, Nuculavus arcuata and Nuculavus menuda, are established; others are present but available material is insufficient to formally define them. These molluscs are subsidiary elements of gastropod-dominated assemblages from two intervals in the Laborcita Formation. Dark gray shale/siltstone lithologies near Tularosa are dominated by nuculoids, whereas gray to tan limestone and calcareous shale strata in La Luz Canyon contain a more diverse pelecypod assemblage that includes Myalina (Orthomyalina) subquadrata, Permophorus, AstarteIla and Wilkingia in addition to several nuculoid taxa. Only two of the 15 pelecypod taxa treated here occur at both localities, reflecting considerably different environmental conditions in which the two assemblages lived. Most of the nuculoids are small to minute in size. The majority of pelecypod taxa and both scaphopods are species previously known from Middle to Upper Pennsylvanian strata, or are clearly derived from Pennsylvanian species. Aside from the new species noted here, the only "typically Permian" pelecypod with no Pennsylvanian record is Nuculavus levatiformis. In both the Tularosa and La Luz assemblages, infaunal species are far more abundant than epifaunal forms.
- Kues, Barry S., 1991, Some pelecypods and scaphopods from the lower Wolfcampian (Basal Permian) Laborcita Formation, Sacramento Mountains, New Mexico, in: Geology of the Sierra Blanca, Sacramento and Capitan Ranges, New Mexico, Barker, James M.; Kues, Barry S.; Austin, George S.; Lucas, Spencer, G., New Mexico Geological Society, Guidebook, 42nd Field Conference, pp. 231-242.