The fossil record of chondrichthyans (Elasmobranchii, Holocephali) from the Cretaceous–Eocene in Chile: diversity and palaeobiogeographic implications

The biodiversity and biogeographical distribution of chondrichthyans in the North Atlantic and Pacific oceans, as well as their connections with Eurasia and North America, underwent significant changes during the Cretaceous-Palaeogene epochs. However, little is known about these changes in the eastern South Pacific. We conducted a review of the fossil record of chondrichthyans in Chile from the Late Cretaceous to the Eocene. Our analysis reveals the presence of 11 orders, 26 families and 43 genera of chondrichthyans. The Eocene assemblages exhibited greater diversity in genera compared to those from the Maastrichtian and Late Paleocene, both of which showed a similar genus richness, but different taxonomic compositions. Similarity analyses indicate differing order dominances, with Rajiformes and Lamniformes prevalent in the Maastrichtian and Lamniformes in Palaeogene. Despite changes in oceanographic, climatic and tectonic conditions, no significant faunal turnover was observed during the Maastrichtian-Palaeogene transition. The geographic dispersion of some taxa and the similarity in climatic and oceanographic conditions across geographically distant localities containing similar faunal assemblages could explain distribution patterns. Our findings suggest that changes in faunal composition and biogeographic distribution in Chile during the Cretaceous-Palaeogene could be linked to significant past climatic and oceanographic events on global and regional scales.