Lepisosteiformes

The earliest known lepisosteiform is the marine Lepidotes from the Early Jurassic of Germany, which largely shares the original body plan of Ginglymodi shared with Semionotiformes.^[1] However, phylogenetic estimates suggest that the earliest lepisosteiforms diverged from their closest relatives in the Middle Triassic. The most basal lepisosteiform is thought to be Khoratichthys from the Late Jurassic or Early Cretaceous of Thailand, which is thought to have diverged from other members of the group during the Late Triassic.^[5] Other studies suggest that the most basal member is Neosemionotus from the Early Cretaceous of Argentina, which diverged from the rest of the group during the Early Jurassic.^[6]

Numerous early lepisosteiforms (including basal lepisosteiforms such as Khoratichthys and Lanxangichthys, lepidotids such as Isanichthys, and basal lepisosteoids such as Thaiichthys) are known from the Late Jurassic and Early Cretaceous of Thailand and Laos, suggesting that what is now Southeast Asia may have been an important region for early lepisosteiform evolution, and that ginglymodians were the dominant fish in freshwater ecosystems in the region at the time.^[5]

It has been suggested that as is with basal ginglymodians and the Semionotiformes, the earliest lepisosteiforms were marine and independently colonized and diversified in freshwater ecosystems multiple times; first among the Lepidotidae, and then among the Lepisosteoidei. Two independent freshwater colonizations appear to have occurred among the lepisosteioids: one in Southeast Asia and one in West Gondwana. The latter included the Obaichthyidae, close relatives of the gar.^[6]

The ecology of the group including extinct members broader than that of living gars. Members of Lepidotidae in particular are strongly different from modern gars in having bulky bodies, with the large (up to 2 metres (6.6 ft)) lepidotid Scheenstia developing powerful jaws filled with rounded teeth that were likely used to crush shells (durophagy).^[7]

• Order Lepisosteiformes Hay, 1929
  • Genus †Adrianaichthys^[8]
  • Genus †Beiduyu^[9]
  • Genus †Khoratichthys^[5]
  • Genus †Lanxangichthys
  • Genus †Neosemionotus
  • Family †Lepidotidae
  • Suborder Lepisosteoidei López-Arbarello, 2012^[1]
    • Genus †Araripelepidotes
    • Genus †Pliodetes^[10]
    • Genus †Thaiichthys
    • Superfamily Lepisosteoidea López-Arbarello, 2012^[1]
      • Family †Obaichthyidae
      • Family Lepisosteidae