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

FERRARI, S.M

JOURNAL OF SYSTEMATIC PALAEONTOLOGY

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2015 vol. 13 p. 919 - 941

1477-2019

Gastropods are represented in the Early Jurassic of Argentina by three major taxa: Vetigastropoda, Caenogastropoda and Opisthobranchia. The present paper aims at the description of nine new vetigastropod species from the Early Jurassic marine deposits of the Neuquén basin, namely Proconulus? argentinus n. sp., Chartronella atuelensis n. sp., Striatoconulus? axialis n. sp., Guidonia disciformis n. sp., Ambercyclus andinus n. sp., Ambercyclus chilcaensis n. sp., Discohelix sanicoensis n. sp., Cryptaenia sudamericana n. sp. and Cryptaenia globosa n. sp. Other three vetigastropods are reported for the first time in the area, such as 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 rothi Damborenea & Ferrari, and an undetermined ataphrid species are also retrieved from marine beds of the Neuquén basin. A quantitative palaeobiogeographical analysis using a statistical method (PAST) was performed integrating the available systematic data of the whole marine vetigastropod species recorded thus far from Argentina. The primary results of the analysis displays two clearly discernible palaeobiogeographical units in the Andean region of Argentina. The local vetigastropod species from Neuquén and Chubut basins may be interpreted considering the palaeogeographical control as determinant in the distribution of these gastropod taxa; this regards on the separated 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 also explain the faunal exchange between both basins at that time.