Evidence of large sturgeons in the Paleocene of North America

Abstract Ray-finned fishes comprise nearly half of extant vertebrate species and include several ancient lineages with fossil records that stretch over 200 Myr in time. One these old clades, the sturgeons paddlefishes, is distributed across Northern Hemisphere includes some largest known freshwater fishes. Yet, record this lineage (Acipenseriformes) poor compared to similarly ray-finned fish clades. Here, I describe sturgeon fossils from two geological units North America < 10 younger than Cretaceous-Paleogene boundary. Both come individuals ~1.5 m length. These Paleogene forms establish long history large body size Acipenseriforms reveal were inhabitants ecosystems still recovering extinction.