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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]
The earliest cephalopods, [b] like Nautilus and some coeloids, appeared to be able to propel themselves forwards by directing their jet backwards. [ 42 ] : 289 Because they had an external shell, they would not have been able to generate their jets by contracting their mantle, so must have used alternate methods, such as by contracting their ...
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.
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]
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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.
The creodonts, which first appeared in the Paleocene, were among the first mammals to specialize in carnivory. [141] The coastal region of the southeastern states, like Alabama [142] and Mississippi [143] were covered in seawater and home to the primitive whale Basilosaurus during the Eocene. The diversity of mammalian carnivores on land ...