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Nautilus (from Latin nautilus 'paper nautilus', from Ancient Greek ναυτίλος nautílos 'little sailor') [3] are the ancient pelagic marine mollusc species of the cephalopod family Nautilidae. This is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina .
Furthermore, unlike the extinct ammonoids, the modern nautilus lacks an aptychus, a biomineralized plate which is proposed to act as an operculum which closes the shell to protect the body. However, aptychus-like plates are known from some extinct nautiloids, and they may be homologous to the fleshy hood of a modern nautilus. [3]
Unlike most modern cephalopods, most ancient varieties had protective shells. These shells at first were conical but later developed into curved nautiloid shapes seen in modern nautilus species. It is thought that competitive pressure from fish forced the shelled forms into deeper water, which provided an evolutionary pressure towards shell ...
Nautilus are unable to easily move across areas deeper than 800 metres, and most of their activity occurs at a depth of 100–300 metres deep. [4] Nautilus can occasionally be found closer to the surface than 100 metres, however, the minimum depth they can reach is determined by factors such as water temperature and season. [4]
This is a list of dates associated with the prehistoric peopling of the world (first known presence of Homo sapiens). The list is divided into four categories, Middle Paleolithic (before 50,000 years ago), Upper Paleolithic (50,000 to 12,500 years ago), Holocene (12,500 to 500 years ago) and Modern ( Age of Sail and modern exploration).
The current classification of the Nautilida, in prevalent use, [1] is that of Bernhard Kummel (Kummel 1964) in the Treatise which divides the Nautilida into five superfamilies, the Aipocerataceae, Clydonautilaceae, Tainocerataceae, and Trigonocerataceae, mostly of the Paleozoic, and the later Nautilaceae.
500–1 BC: Basketmaker phase of early Ancestral Pueblo culture begins in the American Southwest. 500 BC–AD 1000: Plains Woodland period on the Great Plains. [3] 300 BC: Mogollon people, possibly descended from the Cochise tradition, appear in southeast Arizona and southwest New Mexico.
Originating from within the bactritoid nautiloids, the ammonoid cephalopods first appeared in the Devonian (circa 409 million years ago (Mya)) and became extinct shortly after Cretaceous (66 Mya). The classification of ammonoids is based in part on the ornamentation and structure of the septa comprising their shells' gas chambers.