Nautilus
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A nautilus is any of the various species within the cephalopod family Nautilidae. This is the sole extant family of the superfamily Nautilaceae, suborder Nautilina, order Nautilida, and subclass Nauti
Nautilus belauensis from Palau
The first and oldest fossil of chambered nautilus displayed at Philippine National Museum.
Nautilus half-shell showing the camerae in a logarithmic spiral
Section cut of a nautilus shell
Ammonoidea
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Ammonoids are extinct, typically coiled-shelled cephalopods composing the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish than they are to nautiluses, whi
Nautilus
…closer to the first cephalopods that appeared about 500 million years ago than the early modern cephalopods that appeared maybe 100 million years later (ammonoids and coleoids). They have a seemingly simple brain, not the large complex brains of octopus, cuttlefish and squid, and had long been assumed to lack…
Pleuroceras solare, Little Switzerland, Bavaria, Germany
A variety of ammonite forms, from Ernst Haeckel's 1904 Kunstformen der Natur (Art Forms of Nature)
Fossil of Parapuzosia seppenradensis, one of the largest known ammonites
Oppelia in association with its aptychi plates