A New Early Campanian Rudist Fauna from San Luis Potosi in Mexico and Its Taxonomic and Stratigraphic Significance

Abstract

A rudist fauna composed of the radiolitids Potosites tristantorresi new genus, new species and Radiolites acutocostata (Adkins), the hippuritids Barrettia cf. ruseae Chubb, Torreites sanchezi (Douvillé), and Vaccinites vermunti Mac Gillavry, plagioptychids, and antillocaprinids is described from a rudist limestone succession in the central Mexican State of San Luis Potosí. The previously known species, one radiolitid from Texas and three hippuritids from the Caribbean Biogeographic Province, indicate the early Campanian. The new genus is a large radiolitid with a coiled and canaliculated left valve. New observations on R. acutocostata and V. vermunti shell morphology and variability are provided. Observations made on well preserved specimens of the latter species clarify the outer shell layer structure of the hippuritids right valve and has taxonomic implications. This is the first report of genus Torreites in Mexico and one of the northernmost records of genus Barrettia, already reported in southern Mexico from Chiapas State. This rudist limestone succession (informally ‘Temazcal limestones’ herein) is an easy-to-recognize cartographical unit; up to now it and Santonian and Turonian units have been mapped as the El Abra Formation in most available geological maps. Recognition of the successive carbonate platform intervals, between El Abra and Cardenas formations, improves the geological mapping and the understanding of the Mexican Gulf western margin evolution during the Late Cretaceous.