The Pliensbachian ammonites of the Algarve Basin (Portugal) and their palaeobiogeographical significance for the “Iberia-Newfoundland” conjugate margins

A review of the Pliensbachian ammonite faunas of the Algarve Basin is given covering their taxonomy, stratigraphy and palaeobiogeography (palaeobiodiversity). This review is based on both an extensive revision of the previously collected and/or published material and on new finds precisely located within the ammonite succession. This new material allows us to clarify the variations within the most abundant species—a new species Reynesocoeloceras elmii nov. sp. is described—and to improve our understanding (palaeobiodiversity, palaeobiogeography and bio- or chrono-stratigraphy) of the two single known Pliensbachian fossiliferous assemblages in the Algarve Basin. The first of these assemblages is relatively diverse and is ascribed to the upper half of the Luridum Subchronozone. The second assemblage is less diversified and probably partly condensed. It is broadly attributed to the upper half of the Stokesi Subchronozone. Despite the newly collected ammonites and extensive prospecting, our knowledge of the Pliensbachian ammonite faunas of the Algarve remains fragmentary. Therefore, it is difficult to propose an incontrovertible extensive palaeobiogeographical interpretation for these faunas, but it seems that Tethyan (Mediterranean) affinities were of major importance whereas there were probably no NW European influences via the Lusitanian Basin.