Cephalopod size

Cephalopods, which include squids and octopuses, vary enormously in size. The smallest are only about 1 centimetre (0.39 in) long and weigh less than 1 gram (0.035 oz) at maturity, while the giant squid can exceed 10 metres (33 ft) in length and the colossal squid weighs close to half a tonne (1,100 lb), making them the largest living invertebrates. Living species range in mass more than three-billion-fold,^{[nb 1]} or across nine orders of magnitude, from the lightest hatchlings to the heaviest adults.^[4] Certain cephalopod species are also noted for having individual body parts of exceptional size.^[5]

Cephalopods were at one time the largest of all organisms on Earth,^[6] and numerous species of comparable size to the largest present day squids are known from the fossil record, including enormous examples of ammonoids, belemnoids, nautiloids, orthoceratoids, teuthids, and vampyromorphids. In terms of mass, the largest of all known cephalopods were likely the giant shelled ammonoids and endocerid nautiloids,^[7] though perhaps still second to the largest living cephalopods when considering tissue mass alone.^[8]

Cephalopods vastly larger than either giant or colossal squids have been postulated at various times. One of these was the St. Augustine Monster, a large carcass weighing several tonnes that washed ashore on the United States coast near St. Augustine, Florida, in 1896. Reanalyses in 1995 and 2004 of the original tissue samples—together with those of other similar carcasses—showed conclusively that they were all masses of the collagenous matrix of whale blubber.^[9]

Giant cephalopods have fascinated humankind for ages. The earliest surviving records are perhaps those of Aristotle and Pliny the Elder, both of whom described squids of very large size.^[10] Tales of giant squid have been common among mariners since ancient times, and may have inspired the monstrous kraken of Nordic legend, said to be as large as an island and capable of engulfing and sinking any ship.^[11] Similar tentacled sea monsters are known from other parts of the globe, including the Akkorokamui of Japan and Te Wheke-a-Muturangi of New Zealand. The Lusca of the Caribbean and Scylla in Greek mythology may also derive from giant squid sightings,^[12] as might eyewitness accounts of other sea monsters such as sea serpents.^[13]

Cephalopods of enormous size have featured prominently in fiction.^[14] Some of the best known examples include the giant squid from Jules Verne's 1870 novel Twenty Thousand Leagues Under the Seas and its various film adaptations; the giant octopus from the 1955 monster movie It Came from Beneath the Sea; and the giant squid from Peter Benchley's 1991 novel Beast and the TV film adaptation of the same name.

Due to its status as a charismatic megafaunal species, the giant squid has been proposed as an emblematic animal for marine invertebrate conservation.^[15] Life-sized models of the giant squid are a common sight in natural history museums around the world,^[16] and preserved specimens are much sought after for display.^[17]

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