Taxonomical diversity and palaeobiogeographical affinity of belemnites from the Pliensbachian - Toarcian GSSP (Lusitanian Basin, Portugal)

<p>For the first time, high-resolution analysis of the Late Pliensbachian - Early Toarcian belemnite assemblages from the Peniche section (Lusitanian Basin) is presented. The systematic analysis allowed the recognition of eight taxa of the suborder Belemnitina, previously reported from contemporaneous NW Tethyan and Arctic sections. The presence of <i>Bairstowius amaliae</i> sp. nov. in the Late Pliensbachian (Emaciatum Zone) represents a novelty since hitherto the genus <i>Bairstowius</i> was only known from Late Sinemurian and Early Pliensbachian deposits.  Additionally, the replacement of <i>Bairstowius amaliae</i> by <i>Catateuthis longiforma</i>,<i> </i>during the latest Pliensbachian, suggests an evolutionary relationship between the two taxa. This relationship suggests a new scenario for the subsequent development of endemic Toarcian Boreal-Arctic faunas, characterised by the occurrence of <i>Catateuthis</i>. </p> <p>The comparison of the Peniche belemnite fauna with coeval faunas from the Mediterranean/Submediterranean and Euro-Boreal domains indicates taxonomic uniformity during the Late Pliensbachian – Early Toarcian (Emaciatum and Polymorphum zones), in the NW Tethys. Despite the lack of a marked taxonomic turnover, the Pliensbachian-Toarcian boundary corresponds to a slight decrease in diversity observed not only in the Lusitanian Basin but also in coeval NW European basins. Ordination and cluster analyses indicate that the largest changes in belemnite diversity and palaeogeographic distribution occurred rather during the Toarcian Oceanic Anoxic Event (base of Levisoni Zone). This event is marked by the extinction of taxa, affecting more severely the Mediterranean/Submediterranean domain and resulting in a provincial differentiation amongst NW European and Arctic belemnite faunas.</p>