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
edentuloussuspension-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".[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 feedingLeedsichthys, which is estimated to have reached a maximum length of around 16 metres (52 ft).[5]
^Gouiric-Cavalli, S.; Arratia, G. (2022). "A new †Pachycormiformes (Actinopterygii) from the Upper Jurassic of Gondwana sheds light on the evolutionary history of the group". Journal of Systematic Palaeontology. 19 (21): 1517–1550.
doi:
10.1080/14772019.2022.2049382.
S2CID248454343.