BARRY S. KUES, ROGER L. BATTEN
Journal of Paleontology 75 (sp54), 1-95, (1 January 2001) https://doi.org/10.1666/0022-3360(2001)75[1:MPGFTF]2.0.CO;2
The lower Desmoinesian part of the Flechado Formation near Taos, New Mexico, contains a diverse marine fauna within predominantly dark gray shale and siltstone facies representing deposition in shallow marine environments adjacent to prograding lobes of a fan delta system. Gastropods are particularly abundant and diverse in a 60-m-thick section south of the town of Talpa; 157 species are described in this paper, including 19 new species and two new genera. New species are Euphemites hermosus, Luciellina ocultabanda, Spiroscala georgiannae, Glabrocingulum (Glabrocingulum) globosum, G. (Ananias) talpaensis, Worthenia legrandi, Cyclites diminutus, Platyzona hespera, Anomphalus? blancus, Stegocoelia (Donaldospira) taosensis, S. (Hypergonia) hoffmani, S. (H.) agraciada, Bicuerda procolumnare, new genus and species; Hermosanema varium, new genus and species, Pseudozygopleura (Stephanozyga) granda, P. (S.) lisaspira, Hemizyga (Hemizyga) larga, Strobeus immanis, and Meekospira delgada. Species of Pleurotomarioidea, Neritoidea, Trochoidea, and Murchisonioidea comprise 64 percent of the total gastropod specimens, with most specimens of each of the last three groups being contributed by large numbers of one or two very abundant species. The 20 most abundant species are represented by about 65 percent of all specimens, whereas 62 species (39 percent of total species richness, but only 1.1 percent of all specimens) are represented by six or fewer specimens, illustrating the significant contribution of rare species to total species richness. The Flechado gastropod fauna contains many species known from Desmoinesian strata in the Midcontinent and Appalachian Basin regions of the U.S.; many elements of Desmoinesian gastropod assemblages were distributed widely in shallow marine environments across North America. Potential paleogeographic barriers in the Colorado–New Mexico region, however, may have facilitated evolution of some endemic species in this area.