Devonian cartilaginous fish

Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes). They are currently considered to represent a paraphyletic grade of various fish lineages basal to extant Chondrichthyes, which includes living sharks, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both osteichthyans (bony fish) and chondrichthyans (cartilaginous fish). In general body shape, they were similar to modern sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteians (gars, bowfins).

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.

Orodontiformes is an extinct group of cartilaginous fish, known from the Late Devonian and Carboniferous periods. They are part of Euchondrocephali (Holocephali sensu lato), making their closest living relatives chimaeras. Most members are only known from teeth, which are low and rounded, and designed for crushing prey (durophagy). The group in its totality has been described as "undoubtedly artificial" (i.e. non-monophyletic). Several species of Orodus are known from specimens preserving the body as well as the teeth.

Iniopterygiformes (Originally spelled Iniopterygia and sometimes informally abbreviated as "iniops") is an extinct order of cartilaginous fish known only from the Carboniferous period of the United States. Iniopterygians are characterized by large, superficially wing-like pectoral fins positioned upwards behind the head, from which the name of the group (translated as "nape fin") is derived. Iniopterygians are also noted to possess proportionally large skulls and eyes, armor plates composed of dentin, and "tooth-whorls" of fused teeth. Their elongated pectoral fins bore large, denticle-covered

Nostolepis is an extinct genus of acanthodian fish which lived from the Silurian (Wenlock) to the Middle Devonian (Givetian). Members of the genus include Nostolepis gracilis and Nostolepis striata.

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|212x212px|Life restoration of O. micropterygius

Phoebodontiformes is an extinct group of elasmobranchs (sensu lato), known from the Devonian and Carboniferous periods. It includes the genera Phoebodus, Diademodus and Thrinacodus. Phoebodus and Thrinacodus have slender, elongate bodies. Their teeth are tricuspate (bearing three cusps). Some studies have recovered the group as paraphyletic.