![]() Natural history Reproduction and life cycles They also are indirectly important to humans since they furnish a large part of the diet of sperm whales and smaller whales, seals, fishes, and seabirds. They are eaten in most parts of the world and have been accepted as part of the general diet in North America and northern Europe. The shell of the fossil ammonite Pachydiscus seppenradensis from the Cretaceous measures 205 centimetres (6 feet 8 inches) in diameter it is considered to have been the largest shelled mollusk.Ĭephalopods occur in large numbers and form one of the greatest potential food resources of the oceans. But arm spans of up to nine metres (30 feet) have been reported in Octopus dofleini. The average octopus usually has arms no longer than 30 centimetres (12 inches) and rarely longer than a metre (39 inches). The smallest cephalopod is the squid Idiosepius, rarely an inch in length. dux attains a length of more than 20 metres (60 feet), including the extended tentacles. The giant squids ( Architeuthis species) are the largest living invertebrates A. Except for the nautilus, all living members of the class show great modification and reduction of the characteristic molluscan shell.Ĭephalopods range greatly in size. ![]() The best-known feature of the cephalopods is the possession of arms and tentacles, eight or 10 in most forms but about 90 in Nautilus. The cephalopods agree with the rest of the Mollusca in basic structure, and the ancestors appear to have the closest affinity with the ancestors of the class Gastropoda. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.
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