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Hexanchus Vitulus
The Atlantic sixgill shark (''Hexanchus vitulus'') is a rare species of hexanchid shark found in the Atlantic Ocean. It was formerly described as its own species, but was synonymised with the bigeye sixgill shark The bigeyed sixgill shark (''Hexanchus nakamurai'') is a cow shark of the family Hexanchidae. Its dorsal surface has a brownish-gray color, and is sharply separated from the light coloring of its ventral surface. The eyes are a fluorescent gree ... (''Hexanchus nakamurai''). However, a study published in 2019 resurrected the species on the basis of molecular data. The species can be physically differentiated from the bluntnose sixgill shark (''Hexanchus griseus'') by its much smaller size and position of the dorsal fin in relation to the caudal fin. The Atlantic sixgill shark (''Hexanchus vitulus'') becomes sexually mature at around 1.40 to 1.75 meters. They do not reach lengths much greater than 180 cm. Springer, S., & Waller, R. A. (1969). Hexanchus vitulus, a new ...
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Stewart Springer
Stewart Springer (5 June 190623 August 1991) was an American ichthyologist and herpetologist. He was a world-renowned expert on shark behavior, classification (taxonomy), and population distribution. More than 35 species of sharks, skates, rays, and other creatures are either classified by or named after him. Education Springer was a field naturalist, mostly self-taught. In 1964, 35 years after he dropped out of Butler University, Springer obtained a baccalaureate from George Washington University after having already achieved success in his chosen field of ichthyology. Many colleagues and students addressed him as Dr. on the mistaken assumption that he must have a Ph.D. in biology or an allied field given his status in the world community of ichthyologists. His exceptional interest in animal behavior was apparent early in his life, when at age 22, he identified and described a new species of lizard, '' Cnemidophorus velox'', the plateau striped whiptail. His interest in the wh ...
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Cow Shark
Cow sharks are a shark family, the Hexanchidae, characterized by an additional pair or pairs of gill slits. Its 37 species are placed within the 10 genera: ''Gladioserratus'', ''Heptranchias'', ''Hexanchus'', ''Notidanodon'', ''Notorynchus'', ''Pachyhexanchus'', ''Paraheptranchias'', ''Pseudonotidanus'', ''Welcommia'', and ''Weltonia''.Compagno, L., Dando, M. and Fowler, S. ''Sharks of the World''. Princeton Field Guides Cow sharks are considered the most primitive of all the sharks, as their skeletons resemble those of ancient extinct forms, with few modern adaptations. Their excretory and digestive systems are also unspecialized, suggesting they may resemble those of primitive shark ancestors. A possible hexanchid tooth is known from the Permian of Japan, making the family a possible extant survivor of the Permian-Triassic extinction. Their most distinctive feature, however, is the presence of a sixth, and, in two genera, a seventh, gill slit, in contrast to the five found in ...
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Shark
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the rays. However, the term "shark" has also been used to refer to all extinct members of Chondrichthyes with a shark-like morphology, such as hybodonts and xenacanths. The oldest modern sharks are known from the Early Jurassic. They range in size from the small dwarf lanternshark (''Etmopterus perryi''), a deep sea species that is only in length, to the whale shark (''Rhincodon typus''), the largest fish in the world, which reaches approximately in length. Sharks are found in all seas and are common to depths up to . They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river shark, which can be found in both seawater and fresh ...
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Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe and Asia from the "New World" of the Americas in the European perception of the World. The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Europe and Africa to the east, and North and South America to the west. As one component of the interconnected World Ocean, it is connected in the north to the Arctic Ocean, to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south (other definitions describe the Atlantic as extending southward to Antarctica). The Atlantic Ocean is divided in two parts, by the Equatorial Counter Current, with the North(ern) Atlantic Ocean and the South(ern) Atlantic Ocean split at about 8°N. Scientific explorations of the A ...
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Bigeyed Sixgill Shark
The bigeyed sixgill shark (''Hexanchus nakamurai'') is a cow shark of the family Hexanchidae. Its dorsal surface has a brownish-gray color, and is sharply separated from the light coloring of its ventral surface. The eyes are a fluorescent green while the shark is alive. The body of this shark is small, slim, and fusiform in shape. As the name suggests, this shark has six gill slits, unusual among most shark species. The head is narrow and somewhat flattened, and the mouth contains 5 rows of large, comb-shaped teeth. This shark's single dorsal fin is pushed back towards the caudal fin, and is behind the pelvic fins. The upper caudal fin is much longer than the lower, with a deep notch near the tip. All fins have thin white margins on the edge. In juveniles, the upper caudal fin has a black tip. Measurements Length at birth for this species is 34–45 cm; adults average 1.2 m for both genders, with a maximum of 1.8 m. Mature adults weigh around 20 kg. Range and habitat ...
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Hexanchus
The sixgill sharks are a genus, ''Hexanchus'', of deepwater sharks in the family Hexanchidae. These sharks are characterized by a broad, pointed head, six pairs of gill slits, comb-like, yellow lower teeth, and a long tail. The largest species can grow up to 8 m long and weigh over 600 kg (1320 lb). They are continental shelf-dwelling and abyssal plain scavengers with a keen sense of smell and are among the first to arrive at carrion, together with hagfish and rattails. They show a characteristic rolling motion of the head when feeding. They have been found at depths of up to . Though only two extant species (the bluntnose sixgill shark and the bigeyed sixgill shark) were originally known, a third, the Atlantic sixgill shark, was found to exist. Swimming behavior The bluntnose sixgill shark, ''Hexanchus griseus'', is relatively common to scientists. However, very little information exists about its distribution patterns, migrations and behavior. Data on occurrence ...
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