European charophyte evolution across the Cretaceous–Paleogene boundary

Abstract

The Cretaceous–Paleogene (K/Pg) boundary has traditionally been considered a key moment in charophyte evolution, marked by the extinction of two important Mesozoic families, the Porocharaceae and the Clavatoraceae, and a major turnover within the Characeae. However, new data presented here suggest that one species of the European Porocharaceae (based on gyrogonites) and one species of the Clavatoraceae (based on thalli), persisted into the basal Danian. In addition, a taxonomic revision of the Characeae, coupled with an updated biostratigraphy, shows that this family underwent a step-wise extinction during the latest Cretaceous with only a small number of species becoming extinct at the K/Pg boundary. As a result, changes in charophyte floras around the K/Pg boundary in Europe cannot be considered to represent a major turnover in charophyte evolution. Its effects were more comparable to a normal stage boundary event rather than to a major erathem boundary one. Similar disappearance patterns at the K/Pg boundary have also been recorded in other taxa, including fish and amphibians, showing that aquatic freshwater biotas may somehow be resilient to catastrophic events such as those that occurred during the K/Pg crisis.