Symmoriiformes

Cladoselache ("branch shark") is an extinct genus of shark-like chondrichthyan (cartilaginous fish) from the Late Devonian (Famennian) of North America. It was similar in body shape to modern lamnid sharks (such as mako sharks and the great white shark), but was not closely related to lamnids or to any other modern (selachian) shark. As an early chondrichthyan, it had yet to evolve traits of modern sharks such as accelerated tooth replacement, a loose jaw suspension, enameloid teeth, and possibly claspers.

Stethacanthus is an extinct genus of shark-like cartilaginous fish which lived from the Late Devonian to Late Carboniferous epoch, dying out around 298.9 million years ago. Fossils have been found in Australia, Asia, Europe and North America.

Falcatus is an extinct genus of falcatid chondrichthyan which lived during the early Carboniferous Period in Bear Gulch bay in what is now Montana.

Akmonistion is an extinct genus of cartilaginous fish that lived in the Early Carboniferous. The genus contains a single species, A. zangerli, discovered by Stan Wood in 1982. It is distinguished by an unusual enlarged formation of the dorsal fin, called a "spine-brush complex", of unknown function. This is also found in the better known genus Stethacanthus. Remains have only been found near Bearsden in Scotland, where a complete fossil was uncovered in 1982. It reached in length. The genus name is derived from the Ancient Greek “akmon” (“anvil”) + “istion” (“sail”) referring to the appearance

Cladoselachidae is an extinct family of cartilaginous fishes closely related to, and possibly nested within, Symmoriiformes. They are characterized by having an elongated body with a spine in each of the two dorsal fins.

Symmoriidae is an extinct family of cartilaginous fish belonging to the order Symmoriiformes. Members of the family are known from the Devonian and Carboniferous periods.

Cobelodus is an extinct genus of cartilaginous fish known from the late Carboniferous to the early Permian period. The type specimen, assigned to the genus Styptobasis, was discovered by Edward Drinker Cope in Illinois Basin black coal shales. Rainer Zangerl reassigned S. aculeata in 1973 to the genus Cobelodus, translating to 'needle tooth'. Cope's description was based from a tooth fragment and was compared to the genus Monocladodus. Cobelodus differs from Styptobasis and Monocladodus in the anatomy of its teeth and pectoral fins.

Falcatidae is a family of Paleozoic cartilaginous fish belonging to the order Symmoriiformes. Members of this family include Falcatus, a small fish from the Bear Gulch Limestone of Montana. The family first appeared around the start of the Carboniferous, and there is some evidence that they survived well into the early Cretaceous, though its putative Cretaceous members were also argued to be more likely neoselachians.

Stethacanthidae is an extinct family of prehistoric sharks. It is estimated to have existed approximately between 380 and 300 million years ago. Members of this family are noted for their peculiar dorsal fin.

left|thumb|Tooth assigned to Symmorium Symmorium is an extinct symmoriiform cartilaginous fish from the Devonian and Carboniferous of the United States (Illinois) and Russia. The type species, Symmorium reniforme, was named by Edward Drinker Cope in 1893, with other species assigned to the genus having since been reclassified into other genera such as Petalodus. Symmorium bears close similarity in size and appearance to Stethacanthus but lacks the "spine-brush complex" in place of the first dorsal fin. Some paleontologists think that the two forms represented the males and females of related s