page_title: Basking shark
section_title: Anatomy and appearance
hierarchical_section_title: Basking shark / Anatomy and appearance
caption_attribution_description: English: Male Basking Shark (Cetorhinus maximus).
context_page_description: The basking shark is the second-largest living shark, after the whale shark, and one of three plankton-eating shark species, along with the whale shark and megamouth shark. Adults typically reach 7.9 m in length. It is usually greyish-brown, with mottled skin. The caudal fin has a strong lateral keel and a crescent shape.
  The basking shark is a cosmopolitan migratory species, found in all the world's temperate oceans. A slow-moving filter feeder, its common name derives from its habit of feeding at the surface, appearing to be basking in the warmer water there. It has anatomical adaptations for filter-feeding, such as a greatly enlarged mouth and highly developed gill rakers. Its snout is conical and the gill slits extend around the top and bottom of its head. The gill rakers, dark and bristle-like, are used to catch plankton as water filters through the mouth and over the gills. The teeth are numerous and very small, and often number 100 per row. The teeth have a single conical cusp, are curved backwards, and are the same on both the upper and lower jaws. This species has the smallest weight-for-weight brain size of any shark, reflecting its relatively passive lifestyle.
context_section_description: The largest accurately measured specimen was trapped in a herring net in the Bay of Fundy, Canada, in 1851. Its total length was 12.27 m (40.3 ft), and it weighed an estimated 16 t (16 long tons; 18 short tons). Dubious reports from Norway mention three basking sharks over 12 m (39 ft), the largest at 13.7 m (45 ft), during 1884 to 1905, these are dubious because few anywhere near that size have been caught in the area since. On average, the adult basking shark reaches a length of 7.9 m (26 ft) and weighs about 4.65 t (4.58 long tons; 5.13 short tons). Some specimens still surpass 9–10 m (30–33 ft), but after years of large-scale fishing, specimens of this size have become rare.
  They possess the typical shark lamniform body plan and have been mistaken for great white sharks. The two species can be easily distinguished by the basking shark's cavernous jaw, up to 1 m (3 ft 3 in) in width, longer and more obvious gill slits that nearly encircle the head and are accompanied by well-developed gill rakers, smaller eyes, much larger overall size and smaller average girth. Great whites possess large, dagger-like teeth; basking shark teeth are much smaller 5–6 mm (0.20–0.24 in) and hooked; only the first three or four rows of the upper jaw and six or seven rows of the lower jaw function. In behaviour, the great white is an active predator of large animals and not a filter feeder.
  Other distinctive characteristics include a strongly keeled caudal peduncle, highly textured skin covered in placoid scales and a mucus layer, a pointed snout—distinctly hooked in younger specimens—and a lunate caudal fin. In large individuals, the dorsal fin may flop to one side when above the surface. Colouration is highly variable (and likely dependent on observation conditions and the individual's condition): commonly, the colouring is dark brown to black or blue dorsally, fading to a dull white ventrally. The sharks are often noticeably scarred, possibly through encounters with lampreys or cookiecutter sharks. The basking shark's liver, which may account for 25% of its body weight, runs the entire length of the abdominal cavity and is thought to play a role in buoyancy regulation and long-term energy storage.
caption: Male basking shark
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