THE CERITHIACEA, SUBULITACEA, PYRAMIDELLACEA AND ACTEONACEA OF THE PERMIAN BASIN, WEST TEXAS AND NEW MEXICO WITH A CONSIDERATION OF PERMO-TRIASSIC GASTROPOD DYNAMICS (PALEOBIOLOGY, EVOLUTION)

The Late Permian extinction removed c.96% of all marine species and 54% of marine families and marked the end of the archaeogastropod-dominated Paleozoic gastropod fauna and the beginning of a modern gastropod fauna dominated by mesogastropods and neogastropods. Modern forms also exhibit greater adaptive breadth and occupy a greater variety of trophic roles.; This dissertation discusses the systematics, functional morphology and taphonomy of a group of high-spired gastropods from the Permian Basin area of West Texas and New Mexico, with most from the Glass Mountains of Texas. I also consider the structure of the mass extinction in the Guadelupian and Dzulfian Stages and the impact of the extinction on gastropod diversity dynamics during the late Paleozoic and Early Triassic.; The Ischnoptygmidae fam. nov. from the Upper Leonardian includes Ischnoptygma archensis gen. et. sp. nov. and Ischnoptygma valentini sp. nov. and is distinguished from other families of Subulitacea by the presence of a plate or flange-like columellar fold. New taxa of Cerithiacea are Orthonema columna sp. nov., O. illineatus sp. nov., O. paxillex sp. nov., O. pupa sp. nov., O. telescopium sp. nov., O. tricingulata sp. nov., Metorthonema sinistralis gen. et. sp. nov. and M. distortus sp. nov. New taxa of Subulitacea are Cerauncochilus deformis sp. nov., C. elongatus sp. nov., C. kidderi sp. nov., C. trekensis sp. nov., Strobeus girtyina sp. nov., Soleniscus diminutus sp. nov., S. variabilis sp. nov., Cylindritopsis hamiltonae sp. nov., C. spheroides sp. nov. Meekospira mimia sp. nov. is the lone form of Meekospiridae. New taxa of Pyramidellacea are Donaldina knighti sp. nov., D. gracilis sp. nov., Streptacis inflata sp. nov., and S. pierci sp. nov. The single species of Acteonacea is Girtyspira yoda sp. nov.; The formation of the supercontinent of Pangaea in the late Permian caused a decline in marine provinciality from 12 provinces to 1 province and increased seasonality along the remaining marine shelves. Archaeogastropods appear to suffer preferential extinction in the late Permian compared to mesogastropods, perhaps due to removal of planktotrophic archaeogastropods. An important remaining problem is why the radiation of the adaptively superior mesogastropods was delayed until the Upper Triassic and Jurassic. This pattern suggests that mass extinctions may control diversification and the adoption of novel trophic roles.