Kimmeridgian (Late Jurassic) cold-water idoceratids (Ammonoidea) from southern Coahuila, northeastern Mexico, associated with Boreal bivalves and belemnites

Abstract

Here we present two early Kimmeridgian faunal assemblages composed of the ammonite Idoceras (Idoceras pinonense n. sp. and I. inflatum Burckhardt, 1906), Boreal belemnites Cylindroteuthis cuspidata Sachs and Nalnjaeva, 1964 and Cylindroteuthis ex. gr. jacutica Sachs and Nalnjaeva, 1964, as well as the Boreal bivalve Buchia concentrica (J. de C. Sowerby, 1827). The assemblages were discovered in inner- to outer shelf sediments of the lower La Casita Formation at Puerto Pinones, southern Coahuila, and suggest that some taxa of Idoceras inhabited cold-water environments.