Hybodontiformes

Hybodontiformes, also called hybodonts, are an extinct subset of Elasmobranchii (sharks, skates and rays) which existed from the Devonian to the Cretaceous. They form the group of sharks closest to neoselachians, the clade of modern sharks and rays. Hybodonts were named and are distinguished based on their conical tooth shape. They comprised the main group of Jurassic sharks in Europe and North America. They survived into the Late Cretaceous before going extinct, possibly due to competition from other sharks. Lonchidion was one of the last hybodonts— its distinctive serrated fine spines occur in freshwater deposits from Wyoming alongside the fossils of the last dinosaurs, including Tyrannosaurus rex and Triceratops.Hybodontiformes are identified in the fossil record predominantly based on distinct teeth and fin spines. They were known to live in both fresh and salt water environments.