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Cladoselache is an extinct genus of shark-like chondrichthyan (cartilaginous fish) from the Late Devonian 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 shark.
A spiracle is a small hole found behind each eye. These can be tiny and circular, such as found on the nurse shark (Ginglymostoma cirratum), to extended and slit-like, such as found on the wobbegongs (Orectolobidae). Many larger, pelagic species, such as the mackerel sharks (Lamnidae) and the thresher sharks (Alopiidae), no longer possess them.
The genus name, Dracopristis, is derived from the Latin words draco, meaning ' dragon ', and pristis, meaning ' shark '. [5] The dorsal spines, facial denticles, and rows of teeth have been suggested to give the animal a "dragon-like" appearance, [2] [3] [5] and -pristis is a common suffix given to shark-like fishes.
The most ancient types of shark-like fish date back to 450 million years ago, during the Late Ordovician period, and are mostly known by their fossilized teeth and dermal denticles. [5] However, the most commonly found fossil shark teeth are from the Cenozoic era (the last 66 million years).
Shark teeth similar to modern hexanchids and echinorhinids are known from Devonian deposits in Antarctica and Australia, as well as Permian deposits in Japan. If these are in fact hexanchids, this may be the only extant order of elasmobranchs to have survived the Permian extinction (and by extension, the oldest extant order of elasmobranchs).
Unlike traditional scales, sharks have placid scales, known as denticles. Denticles are V-shaped and are made of layers of dentine and a surface of enamel. [24] Riblets are sockets in the shark's skin which hold the denticles. [22] These denticles on the skin allow for the shark to move quietly, swiftly, and almost effortlessly.
The whale shark (Rhincodon typus) is a slow-moving, filter-feeding carpet shark and the largest known extant fish species. The largest confirmed individual had a length of 18.8 m (61.7 ft). [ 8 ] The whale shark holds many records for size in the animal kingdom, most notably being by far the most massive living non-cetacean animal.
Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and rays (Neoselachii) as part of the clade Euselachii. They are distinguished from other chondrichthyans by ...