Ginglymodi

The fossil record of ginglymodians goes back at least to the Anisian stage of the Triassic period, over 240 million years ago.[8] Eosemionotus is one of the earliest ginglymodians. Acentrophorus, another taxon from the Wuchiapingian stage of the late Permian, and Paracentrophorus from the Early Triassic epoch, could be even earlier members of the group. Ginglymodi was diverse and widespread during the Mesozoic era, but they represent a depauperate lineage today. The group first evolved in marine environments, but several lineages made separate transitions into freshwater environments.[9] Ginglymodi underwent substantial diversification during the Late Triassic and the Late Jurassic.[10] The earliest known gars are from the Late Jurassic.[11] Ginglymodians underwent a major decline during the mid-Cretaceous, eventually leaving gars as the only surviving members of the group.[10] Gar fossils have been found on all continents except Australia and Antarctica. Only seven species exist today, distributed in the freshwater systems of North America.[11]