Lower Cretaceous ammonites from the Neuquén Basin, Argentina: The neocomitids of the Pseudofavrella angulatiformis Zone (upper Valanginian)

Abstract

The Pseudofavrella angulatiformis Zone (upper Valanginian) of the Agrio Formation in the Neuquén Basin, Argentina, is characterized exclusively by a complex sequence of neocomitid faunas that are sandwiched between the olcostephanids of the underlying Viluceras permolestus Subzone beneath and the holcodiscid faunas of the Holcoptychites neuquensis Zone above (lowermost Hauterivian). Three successive neocomitid genera, Pseudofavrella, Chacantuceras and Decliveites gen. nov., characterize three subzones. Over half the taxa are new: Pseudofavrella robusta, P. sp. nov. 1 and 2, Chacantuceras casanuestraense, Chacantuceras coniunctum, Decliveites crassicostatus, and Decliveites agrioensis.