Pachycormiformes

Pachycormiformes Temporal range: Early Jurassic - Late Cretaceous, Toarcian–Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N
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]
Diphyodontidae Jordan, 1923 Erisichtheidae Cope, 1877b Microlepidoti Zittel, 1887 Pelecopteridae Cope, 1875 Protosphyraenidae Lydekker, 1889 Sauropsidae Cope, 1877a Saurotomini [Saurostomini] Bonaparte, 1846 corrig. Bonaparte 1850a

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 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]

• 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^[9]
  • Orthocormus Weitzel, 1930
  • Protosphyraena Leidy, 1857
  • Simocormus Maxwell et al., 2020
• Asthenocorminae Cooper et al., 2022
  • Germanostomus Cooper et al., 2022^[8]
  • 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).^[10]