Corals, molluscs, and paleogeography of late Jurassic strata of the Cerro Pozo Serna, Sonora, Mexico

Abstract

Jurassic strata of late Oxfordian to early Kimmeridgian age are reported from the Cerro Pozo Serna, northwest-central Sonora, Mexico. The presence of these marine strata greatly alters previous paleogeographic reconstructions of the Tethyan embayment in this area. Approximately 60% of the Sonorian molluscan fauna has been previously reported from Jurassic horizons in the Gulf of Mexico and west Texas regions. The remainder of the molluscs have previously been reported from either the western interior United States or Canada. The Pozo Serna faunas seem to be zoogeographically transitional between communities present in the southern North American Tethyan realm and regions within the central North American Tethyan realm. Additionally, the Pozo Serna fauna greatly resembles contemporaneous communities reported from the Jurassic of Morocco. Corals from the Sonorian Jurassic prove to be, in large part, conspecific with well-known central European and Algerian reef-building species. The scleractinian Lepidophylliopsis gen. nov. and Macgeopsis sonorensis sp. nov. are described from central Sonora.