Original paper

The distribution of Thorolamellaptychus and some rare Mortilletila-mellaptychus (Cephalopoda) in the Valanginian of southeast France and Spain

Vašíček, Zdeněk; Janssen, Nico M.M.; Klein, Jaap

Abstract

In the last years several Early Cretaceous aptychi were collected from ammonite-controlled sections of the Vocontian Basin (southeast France) and in the one locality in the Subbetic Zone of Spain (Tornajo). Herein, we describe four species of lamellaptychi, i.e.the genus Thorolamellaptychus, including: Th.aplanatus,Th.symphysocostatus, Th .subangulatus and Th.lombardicus. All of them occur in the Lower Valanginian and in the lower part of the Upper Valanginian. Th.symphysocostatusis especially abundant in the transitional beds of the Lower/Upper Valanginian. Together with the latter genus, the far less well-known species Mortilletilamellaptychus angulodidayi and M. undulatiformis occur. In respect of the morphology of their early ribbing, Didayilamellaptychus angulodidayi is now included in Mortilletilamellaptychus. The remarkable abundance of valves of Th. symphysocostatus around the Early/Late Valanginian boundary can be considered as a "Symphysocostatus Event".

Keywords

symphysocostatus eventmortilletilamellaptychusthorolamellaptychusvocontian basinsubbetic zonelamellaptychi