Pachycormiformes

Pachycormiformes is an extinct order of marine ray-finned fish known from the Early Jurassic to the end of the Cretaceous. Depending on the treatment, it only includes a single family, Pachycormidae, or two families: the mostly filter-feeding Pachycormidae and the carnivorous Protosphyraenidae. 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 == left|thumb|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". Pachycormiformes varied substantially in size, from medium-sized fishes around 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 .