The Neogene record of cartilaginous fishes (Chondrichthyes: Holocephali, Elasmobranchii) from northern Chile: A review and identification guide

Abstract

The abundance of fossil sharks and other cartilaginous fishes in northern Chile is widely known. Fossil sites such as the Bahia Inglesa Formation were affected by intense exploitation by fossil traffickers, which caused the departure of numerous specimens that are currently in foreign collections. Fortunately, this has decreased in the last decade and the study of Chilean specimens has been increasing. This study seeks to synthesize and update our knowledge about fossil chondrichthyans from northern Chile, specifically during the Neogene, offering a review of the species mentioned in the literature, along with key characters that can help in their identification. In this way, we seek to generate a guide for the classification of dental elements, and outline future works that can validate some of these records. This is important if we take into account that a third of the records mentioned in the literature remain unconfirmed, due to the lack of adequate descriptions or images to validate the assignments. Furthermore, most confirmed records can only be validated at the genus level. Despite these difficulties, we identified 42 chondrichthyan taxa for the region and discuss their reliability. Of these only 28 can be confirmed based on the current evidence which, based on a rarefaction analysis, we estimate could represent 76% of the potential taxa to be discovered for the Neogene of northern Chile. This highlight the need for more studies on all unconfirmed taxa and to continue exploring these basins.