Ginglymodi Temporal range: Middle Triassic (Anisian)–present PreꞒ Ꞓ O S D C P T J K Pg N Possible Permian records
Spotted gar (Lepisosteus oculatus)
Macrosemimimus fegerti (Semionotiformes) from the Upper Jurassic of Germany
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Infraclass:	Holostei
Clade:	Ginglymodi Cope, 1871
Subgroups
†Diandongichthys †Sangiorgioichthys †Ticinolepis †Kyphosichthyiformes Sun & Ni.2018 Kyphosichthys Luoxiongichthys Yudaiichthys Fuyuanichthys Lashanichthys Neoginglymodi López-Arbarello & Sferco, 2018[1] †Semionotiformes Lepisosteiformes

Ginglymodi is a clade of ray-finned fish containing modern-day gars (Lepisosteidae) & their extinct relatives (including the family Lepidotidae) in the order Lepisosteiformes, the extinct orders Semionotiformes and Kyphosichthyiformes, and various other extinct taxa. Ginglymodi is one of the two major subgroups of the infraclass Holostei, the other one being Halecomorphi, which contains the bowfin and eyespot bowfin and their fossil relatives.^[1][2]

Fossil record

The fossil record of ginglymodians goes back at least to the Anisian stage of the Triassic period, over 240 million years ago.^[3] Eosemionotus is one of the earliest ginglymodians. Acentrophorus, another taxon from the Middle and 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.^[4] The basal ginglymodian order Kyphosichthyiformes is known from a few genera from the Triassic of China, many of which have deep bodies.^[5]

Ginglymodi underwent substantial diversification during the Late Triassic and the Late Jurassic, with the Lepisosteiformes and Semionotiformes having likely diverged during the Middle Triassic.^[6] Early non-gar ginglymodians of all groups, but especially early lepisosteiforms, show heavy morphological convergence with modern cypriniforms (carp and relatives), suggesting that they may have had a similar ecological niche. Notably, molecular evidence suggests that the cypriniforms may have originated and diversified around the same time and place (Late Jurassic and Early Cretaceous Southeast Asia) that the similar freshwater ginglymodians showed major diversification.^[7] Eventually, some ginglymodians evolved a more predatory lifestyle, with the earliest known true gars from the Late Jurassic.^[8] Ginglymodians underwent a major decline during the mid-Cretaceous, eventually leaving gars as the only surviving members of the group.^[6] 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.^[8]

Phylogeny

Phylogenetic relationships of Ginglymodi to other living neopterygian fish.

Phylogenetic relationships among different groups of ginglymodians (cladogram after Xu & Ma 2023):^[9]

References

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