Callovian nautiloids from the Neuquén Basin, Argentina

For the first time Callovian nautiloids from the Neuquén Basin (Argentina) are described. All the material was collected with precise stratigraphic control based on the local ammonite successions. Most specimens belong to Cenoceras sp. A from the Lotena Fm at Picún Leufú (Patagoniensis Z., lower Upper Callovian) and Los Molles Fm at Chacay Melehué (Proximum Z., upper Lower Callovian). Additionally, one specimen assigned to Cenoceras sp. B comes from the Lotena Fm at Picún Leufú (Patagoniensis Z.). Jurassic nautiloids are usually scarce all around the world with respect to ammonites, but in the Neuquén Basin they are very scarce. Our collections of cephalopods have produced some fifteen nautiloids besides more than 5.000 ammonites collected in Late Callovian to Late Tithonian sequences of the Neuquén Basin. This asymmetric pattern of abundance is surely based, at least in part, on the different reproductive strategies of ammonoids and nautiloids.