Ammonoid morphotypes from the upper Albian of the Basque-Cantabrian Basin: palaeoecology and relationship with the sedimentary facies

In this work we present a morphological study of 65 planispiral ammonoid specimens occurring in the stratigraphic succession of the lower upper Albian of the central region of the Basque-Cantabrian Basin, northern Spain. The specimens correspond to the Zones of the ammonoids Hysteroceras varicosum and Mortoniceras inflatum. They are grouped into different morphotypes following the method of “Westerman Morphospace” which suggests diverse habitats for ammonoids, based on shell architecture and shape. The objective of this work is to check the likely correspondence of the suggested habitats with the information given by sedimentology. Accordingly, it has been possible to establish a distribution of the ammonoid ecomorphotypes demersal, nektonic, planktonic and vertical migrant, from shallow (neritic) to deeper marine areas (epipelagic to mesopelagic). The distribution of these ecomorphotypes with different bathimetric affinities is in agreement with the environmental interpretation of sedimentological data.