Pachycormiformes

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 ), 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.

Description
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". Pachycormiformes varied substantially in size, from medium-sized fishes around 40-111 cm in length like the macropredator Pachycormus, to the largest known ray-finned fish, the suspension feeding Leedsichthys, which is estimated to have reached a maximum length of around 16 m.

Relationships
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.

Taxonomy
Taxonomy according to Cooper et al. (2022):


 * Euthynotus Wagner, 1860
 * Haasichthys Delsate, 1999
 * Notodectes Dolgopol de Saez, 1949
 * Pseudoasthenocormus
 * Sauropsis Agassiz, 1843
 * Hypsocorminae Vetter, 1881
 * Australopachycormus Kear, 2007
 * Hypsocormus Wagner, 1860
 * Kaykay Gouiric-Cavalli & Arratia, 2022
 * Orthocormus Weitzel, 1930
 * Protosphyraena Leidy, 1857
 * Simocormus Maxwell et al., 2020
 * Asthenocorminae Cooper et al., 2022
 * Germanostomus Cooper et al., 2022
 * Ohmdenia Hauff, 1953
 * Pachycormus? Agassiz, 1833
 * Saurostomus Agassiz, 1843
 * Suspension-feeding clade
 * Asthenocormus Woodward, 1895
 * Bonnerichthys Friedman et al., 2010
 * Leedsichthys Woodward, 1889
 * Martillichthys Liston, 2008
 * Rhinconichthys Friedman et al., 2010

Cladistics according to Friedman et al. (2010).