Pachycormiformes

Pachycormiformes Temporal range: Early Jurassic - Late Cretaceous,
Skeleton of Pachycormus
Skeleton of Orthocormus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	†Pachycormiformes Berg 1937
Family:	†Pachycormidae Woodward, 1895
Type genus
Pachycormus Agassiz, 1833
Genera
See text

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. Their exact relations with other fish are unclear, but they are generally considered to be teleosteomorphs, more closely related to teleosts than to Holostei. Pachycormiformes are morphologically diverse, containing both tuna and swordfish-like carnivorous forms, as well as edentulous suspension-feeding forms, with the latter including the largest ray finned fish known to have existed, Leedsichthys, with an estimated maximum length of 16 metres.

Synapomorphies

Size comparison of various species of Pachycormiform fish

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"

Relationships

Pachycormiformes are generally interpreted as 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.

Gallery

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  Reconstruction of Protosphyraena perniciosa

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  Life restoration of Leedsichthys

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  Life restoration of Ohmdenia

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  Life restoration of Bonnerichthys

Taxonomy

• Order †Pachycormiformes Berg 1937 [Pachycormida]
  • Family †Pachycormidae Woodward 1895 [Protosphyraenidae Cope 1875; Erisichtheidae Cope 1877; Pelecopteridae Cope 1875; Saurostomini Bonaparte 1846 corrig. Bonaparte 1850a; Sauropsidae Cope 1877a; Microlepidoti Zittel 1887] Taxonomy according to
    • Genus †Euthynotus Wagner, 1860 [Heterothrissops le Sauvage 1875; Pseudothrissops Sauvage 1875]
    • Genus †Haasichthys Delsate, 1999
    • Genus †Hypsocormus Wagner, 1860
    • Genus †Kaykay Gouiric-Cavalli & Arratia, 2022
    • Genus †Notodectes Dolgopol de Saez, 1949
    • Genus †Ohmdenia Hauff, 1953
    • Genus †Pachycormus Agassiz, 1833 non Coville ex Standley 1923 [?Pachylepis Quenstedt 1858 non Pander 1856; ?Lycodus Quenstedt 1856]
    • Genus †Pseudoasthenocormus
    • Genus †Sauropsis Agassiz, 1843
    • Genus †Saurostomus Agassiz, 1843
    • Genus †Simocormus Maxwell et al., 2020
    • Macrocarnivore clade
      • Genus †Australopachycormus Kear, 2007
      • Genus †Orthocormus Weitzel, 1930
      • Genus †Protosphyraena Leidy, 1857 [Erisichthe Cope 1872; Pelecopterus Cope 1875]
    • Suspension feeding clade
      • Genus †Asthenocormus Woodward, 1895 [Agassizia Vetter 1881 non Agassiz & Desor 1847 non Behr 1870 non Yoshiyasu 1987]
      • Genus †Bonnerichthys Friedman et al., 2010
      • Genus †Leedsichthys Woodward, 1889 [Leedsia Woodward 1890]
      • Genus †Martillichthys Liston, 2008
      • Genus †Rhinconichthys Friedman et al., 2010

Cladistics according to Friedman et al. (2010).

Pachycormiformes	†Euthynotus         †Hypsocormus insignis       †"Hypsocormus" tenuirostris       †Orthocormus       †Australopachycormus     †Protosphyraena               †Pachycormus   Suspension feeding clade     †Asthenocormus titanius     †Martillichthys renwickae         †Bonnerichthys gladius       †Leedsichthys problematicus     †Rhinconichthys taylori

Sources/external links

• http://www.courtenaymuseum.ca/paleo/paleo/pachycor.html
• https://web.archive.org/web/20081025044133/http://www.palaeos.com/Vertebrates/Units/100Neopterygii/100.600.html
• Sepkoski, Jack (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology. 363: 1–560. Retrieved 2011-05-17.
• "Pachycormiformes". Paleobiology Database. Retrieved November 11, 2012.