Early Jurassic marine gastropods from Argentina: a palaeobiogeographical analysis based on Vetigastropoda

Abstract

Gastropods are represented in the Early Jurassic of Argentina by Vetigastropoda, Caenogastropoda and Opisthobranchia. The present paper describes nine new vetigastropod species from the Early Jurassic marine deposits of the Neuquén Basin: Proconulus? argentinus sp. nov., Chartronella atuelensis sp. nov., Striatoconulus? axialis sp. nov., Guidonia disciformis sp. nov., Ambercyclus andinus sp. nov., Ambercyclus chilcaensis sp. nov., Discohelix sanicoensis sp. nov., Cryptaenia sudamericana sp. nov. and Cryptaenia globosa sp. nov. Another three vetigastropods are reported for the first time in this region – Chartronella gradata Ferrari, Ataphrus mulanguiniensis Ferrari and Colpomphalus? aff. musacchioi Ferrari – extending their palaeobiogeographical distributions in the Andean region of Argentina. Lithotrochus humboldtii (von Buch), Lithotrochus rothi Damborenea & Ferrari, and an undetermined ataphrid species were also retrieved from marine beds of the Neuquén Basin. A quantitative palaeobiogeographical analysis was performed integrating available data on the entire marine vetigastropod species thus far recorded from Argentina. The primary results of the analysis show two clearly discernible palaeobiogeographical units in the Andean region of Argentina. The local vetigastropod species from the Neuquén and Chubut basins may be interpreted considering palaeogeographical control as a determinant in the distribution of these taxa, including the separate evolution of the Neuquén basin until the late Pliensbachian. However, a shallow marine connection between the Neuquén and Chubut basins along the Palaeo-Pacific seaway during the late Pliensbachian–early Toarcian may explain faunal exchange between both basins at that time.