A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through convergent evolution they have independently evolved external superficial fish-like body plans ideal for their marine environments, including most numerously fish, but also mammals such as cetaceans, and even extinct ancient marine reptiles such as various known species of ichthyosaurs. Most species have only one dorsal fin, but some have two or three.
Cladoselache is a genus of extinct shark-like chondrichthyan which first appeared in the Devonian period. Growing up to 1.8 metres (5.9 ft) long and roaming the oceans of North America, it is considered to have been a fast-moving and fairly agile predator due to its streamlined body and deeply forked tail. Cladoselache is one of the best known of the early chondrichthyans in part due to the well preserved fossils that were discovered in the Cleveland Shale on the south shore of Lake Erie. In addition to the skeleton, the fossils were so well preserved that they included traces of skin, muscle fibers, and internal organs, such as the kidneys.
Xenacanthus is a genus of prehistoric sharks. The first species of the genus lived in the later Devonian period, and they survived until the end of the Triassic, 202 million years ago. Fossils of various species have been found worldwide.
Dicraeosaurus is a genus of small diplodocoid sauropod dinosaur that lived in what is now Tanzania during the late Jurassic. It was named for the spines on the back of the neck. The first fossil was described by paleontologist Werner Janensch in 1914.
Stethacanthus is an extinct genus of shark-like holocephalians which lived from the Late Devonian to Late Carboniferous epoch, dying out around 298.9 million years ago. Fossils have been found in Asia, Europe and North America.
The rough longnose shark is a little-known deepwater dogfish. This species was described by Samuel Garman in 1906 and originally named Acanthidium hystricosa.
Hybodus is an extinct genus of Chondrichthyans. First appearing towards the end of the Permian period, and disappearing during the Late Cretaceous, during the Triassic, Jurassic, and Cretaceous periods the hybodonts were especially successful and could be found in shallow seas across the world. For reasons that are not fully understood, the hybodonts became extinct near the end of the Late Cretaceous period.
Tristychius is an extinct genus of shark from the Carboniferous period (Visean). Fossils of T. arcuatus, the type and only species, including fin spines have been found in Scotland.
Climatius is an extinct genus of spiny shark. Fossils have been found in both Europe and North America.
Pholidophorus is an extinct genus of teleost fish from the Triassic period of Africa, Europe, and South America.
Hypsidoris is an extinct genus of catfish, classified within its own family Hypsidoridae, from the Eocene epoch of North America.
Berycopsis is an extinct genus of beardfish from the Cretaceous period. Fossils are known from England.
Strunius is an extinct genus of lobe-finned fish from the Late Devonian period of Germany.
The prickly dogfish is a poorly known species of dogfish shark in the family Oxynotidae, inhabiting temperate Australian and New Zealand waters. Reaching a length of 75 cm (30 in), this brown to gray shark has a very thick body with a prominent "humpback" and extremely rough skin. It is further characterized by two enormous, sail-like dorsal fins placed relatively close together. Both dorsal fins have a spine embedded mostly within the fleshy leading portion of the fin; the first dorsal spine is tilted forward.
The Java stingaree is a species of stingray in the family Urolophidae, known only from a single female specimen 33 cm (13 in) long caught off Jakarta, Indonesia. This species is characterized by an oval-shaped pectoral fin disc longer than wide, and a tail with a dorsal fin in front of the stinging spine and a caudal fin. It is brown above, with darker and lighter spots. The International Union for Conservation of Nature has listed the Java stingaree as critically endangered; it has not been recorded since its discovery over 150 years ago, and its range is subject to heavy fishing pressure and habitat degradation.
Centropyge multicolor, the multicolor angelfish or pearlback angelfish, is a species of marine ray-finned fish, a marine angelfish belonging to the family Pomacanthidae. It is from the Pacific Ocean that sometimes makes its way into the aquarium trade. It grows to a size of 9 cm in length.
The snake mackerel is a species of fish in the monotypic genus Gempylus, belonging to the family Gempylidae. It is found worldwide in tropical and subtropical oceans between the latitudes of 42°N and 40°S; adults are known to stray into temperate waters. It is found to a depth of 600 meters. Populations of the snake mackerel from the Atlantic and the Indo-Pacific differ in vertebral count and number of first dorsal fin spines, and so may represent separate species.
The Upper Zambezi labeo is a species of cyprinid fish of the genus Labeonative to southern Africa.
The pearl stingray is a little-known species of stingray in the family Dasyatidae, found in shallow coastal waters from Mauritania to Angola. Growing to 30 cm (12 in) across, this species has a rounded pectoral fin disc with a pointed snout, and a wide band of dermal denticles over the back in adults. It closely resembles and is often confused for the much larger daisy stingray ; both species are characterized by the presence of an enlarged, nacreous denticle in the middle of the back called a "pearl spine". The International Union for Conservation of Nature (IUCN) does not yet have enough information to assess the pearl stingray's conservation status, but it is likely that most of the historically reported fishery catches of the daisy stingray were in fact of this species.
Dorsetichthys is an extinct genus of stem-teleost ray-finned fish from the Early Jurassic period of Europe.
