Early Jurassic marine gastropods from Argentina: Vetigastropoda from the Neuquén Basin and their palaeobiogeographical significance

FERRARI, S.M.; DAMBORENEA, S.E.

Mendoza

Congreso; 4th International Palaeontological Congress; 2014

International Palaeontological Association

Gastropod species are represented in the Early Jurassic of Argentina by four major taxa: Vetigastropoda, Caenogastropoda, Ptenoglossa and Opisthobranchia. The present approach aims at the characterization of eight vetigastropod species from the Early Jurassic marine deposits of the Neuquén basin: Proconulus sp., Chartronella sp., Guidonia sp., Ambercyclus sp. 1, Ambercyclus sp. 2, Discohelix sp., Ptychomphalus sp. 1 and Ptychomphalus sp. 2. Other three previously described vetigastropods are reported for the first time in the area: Chartronella gradata Ferrari, Ataphrus mulanguiniensis Ferrari and Colpomphalus? aff. musacchioi Ferrari, extending also their palaeobiogeographical distribution in the Andean region of Argentina. Lithotrochus humboldtii (von Buch), Lithotrochus rothii Damborenea & Ferrari, Ptychomphalus sp., and an undetermined ataphrid species are also known from marine beds in the Neuquén basin. A quantitative palaeobiogeographical analysis was performed, integrating the available systematic data of all Early Jurassic marine vetigastropod species recorded thus far from Argentina. The data include members of 11 vetigastropod families recorded from 28 marine localities in the Neuquén and Chubut basins. The primary results of the analysis indicate that for the late Pliensbachian-early Toarcian interval two palaeobiogeographical units can be recognized in the Andean region of Argentina, in the Neuquén and Chubut basins respectively. The vetigastropod distribution patterns and local high endemism in both areas of the Andean region of Argentina are most probably related to an independent and separate evolution of the Neuquén basin (s.s.) since the early Hettangian to the early Pliensbachian, and the absence of marine deposits in Chubut at that time. However, a shallow marine connection between the Neuquén and Chubut basins during the late Pliensbachian-early Toarcian through the Palaeo-Pacific seaway may explain the coincident occurrence of some vetigastropod species in both palaeogeographical areas. These new and updated taxonomic data greatly improve our palaeobiogeographical knowledge along the Andean region of South America and the southern hemisphere.