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Extinct order of ray-finned fishes From Wikipedia, the free encyclopedia
Pachycormiformes is an extinct order of marine ray-finned fish known from the Early Jurassic to the end of the Cretaceous. It only includes a single family, Pachycormidae. They were characterized by having serrated pectoral fins (though more recent studies demonstrated that fin shape diversity in this group was high[2]), reduced pelvic fins and a bony rostrum. Pachycormiformes are morphologically diverse, containing both tuna and swordfish-like carnivorous forms, as well as edentulous suspension-feeding forms.
| Pachycormiformes Temporal range: Early Jurassic - Late Cretaceous, | |
|---|---|
.JPG) | |
| Skeleton of Pachycormus | |
| |
| Skeleton of Orthocormus | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Infraclass: | Teleosteomorpha |
| Division: | †Aspidorhynchei |
| Order: | †Pachycormiformes Berg 1937 |
| Family: | †Pachycormidae Woodward, 1895 |
| Type genus | |
| Pachycormus Agassiz, 1833 | |
| Genera | |
|
See text | |
| Synonyms[1] | |
| |
Pachycormiformes are united by "a compound bone (rostrodermethmoid) forming the anterodorsal border of the mouth; a reduced coronoid process of the mandible; absence of supraorbitals associated with a dermosphenotic defining the dorsal margin of the orbit; two large, plate-like suborbital bones posterior to the infraorbitals; long, slender pectoral fins; asymmetrical branching of pectoral fin lepidotrichia; considerable overlap of the hypurals by caudal fin rays (hypurostegy); and the presence of distinctive uroneural-like ossifications of the caudal fin endoskeleton".[3] Pachycormiformes varied substantially in size, from medium-sized fishes around 40–111 centimetres (1.31–3.64 ft) in length like the macropredator Pachycormus,[4] to the largest known ray-finned fish, the suspension feeding Leedsichthys, which is estimated to have reached a maximum length of around 16 metres (52 ft).[5]
Pachycormiformes are generally interpreted as basal members of Teleosteomorpha, the group that includes all fish more closely related to modern teleosts than to Holostei (the group containing bowfin and gars), often they have been considered to be the sister group of the Aspidorhynchiformes.[6][7]
Taxonomy according to Cooper et al. (2022):[8]
Cladistics according to Friedman et al. (2010).[10]
| Pachycormiformes | |
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