A Late Devonian actinopterygian suggests high lineage survivorship across the end-Devonian mass extinction

An actinopterygian fossil with unexpected anatomical features from 7 million years before the end-Devonian mass extinction suggests complex patterns of divergence and diversification around the Devonian/Carboniferous boundary for ray-finned fishes. Many accounts of the early history of actinopterygians (ray-finned fishes) posit that the end-Devonian mass extinction had a major influence on their evolution. Existing phylogenies suggest this episode could have acted as a bottleneck, paring the early diversity of the group to a handful of survivors. This picture, coupled with increases in taxonomic and morphological diversity in the Carboniferous, contributes to a model of explosive post-extinction radiation. However, most actinopterygians from within a roughly 20-million year (Myr) window surrounding the extinction are poorly known, contributing to uncertainty about the meaning of these patterns. Here, we report an exceptionally preserved fossil from 7 Myr before the extinction that reveals unexpected anatomical features. Palaeoneiros clackorum gen. et sp. nov. nests within a clade of post-Devonian species and, in an expanded phylogenetic analysis, draws multiple lineages of Carboniferous actinopterygians into the Devonian. This suggests cryptic but extensive lineage diversification in the latest Devonian, followed by more conspicuous feeding and locomotor structure diversification in the Carboniferous. Our revised model matches more complex patterns of divergence, survival and diversification around the Devonian/Carboniferous boundary in other vertebrate clades. It also fundamentally recalibrates the onset of diversification early in the history of this major radiation.

Automated summary

An exceptionally preserved fossil from 7 million years before the end-Devonian mass extinction reveals unexpected anatomical features. This suggests complex patterns of divergence and diversification around the Devonian/Carboniferous boundary, as well as conspicuous feeding and locomotor structure diversification in the Carboniferous.