Lower Cretaceous ammonoids from the Neuqu?en Basin, Argentina: The late Hauterivian Paraspiticeras and associated faunas

The Paraspiticeras groeberi Zone (upper Hauterivian) is one of the five ammonoid biozones previously recognized in the Agua de la Mula Member of the Agrio Formation in the Neuquen Basin of west-central Argentina. However, the ammonoid faunas of this zone and the beds immediately below, corresponding to the upper levels of the current Crioceratites diamantensis Zone, remain poorly known. Extensive collections now allow us to recognize a diverse endemic ammonoid fauna. After an exhaustive taxonomic and stratigraphic review, the Paraemericiceras argentinense and Paraspiticeras bituberculatum Zones are proposed to replace the P. groeberi Zone and the original index species is now placed in Vutacuracrioceras gen. nov. Vutacuracrioceras groeberi first appears with the earliest Paraemericiceras argentinense gen. et sp. nov. and extends through both zones. It is joined in the Paraspiticeras bituberculatum Zone by the index species and Paraspiticeras sp. aff. P. precrassispinum, Australopseudothurmannia flexuosa gen. et sp. nov. and Hamulinites sp. Based on this new biostratigraphic scheme, the upper Hauterivian in the Neuquen Basin is represented now by six ammonoids zones that can be correlated provisionally with the European standard of the West Mediterranean Province of the Tethyan Realm. (c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

In this study, the Paraspiticeras groeberi Zone was discovered in the Agua de la Mula Member of the Agrio Formation in the Neuquen Basin of west-central Argentina. The newly collected specimens allowed for the recognition of a diverse endemic ammonoid fauna. Based on a taxonomic and stratigraphic review, the Paraemericiceras argentinense and Paraspiticeras bituberculatum Zones are proposed to replace the P. groeberi Zone. This study presents a new biostratigraphic scheme for the upper Hauterivian in the Neuquen Basin.