Ceratosphinctes (Ammonitina, Kimmeridgian) in Mexico: from rare but typical inhabitant of west-Tethyan epioceanic and epicontinental waters to a geographically widespread ammonite genus

Abstract

Two specimens of Ceratosphinctes represent the first record of this taxon in Mexico (Mexican Huasteca), and are interpreted as Cerato-sphinctes rachistrophus amatitlaensis nov. subsp. The subspecies level is used with biogeographic significance, most probably indicating incoming propagules and adaptation to local environmental requirements. Biostratigraphy, based on agreement of the composition of the ammonite assemblage that included C rachistrophus amatitlaensis nov. subsp. and the previous interpretation of ammonite assemblages with Idoceras in Mexico by Villasenor et al., indicates precise correlation with Tethyan records (uppermost-Lower to lowermost-Upper Kimmeridgian). The dispersion pattern available for Ceratosphinctes is interpreted as related to ecospace enlargement during the relative sea-level highstand of the late-Early Kimmeridgian. (c) 2006 Elsevier SAS. All rights reserved.