page_title: Argonaut (animal)
section_title: Classification
hierarchical_section_title: Argonaut (animal) / Classification
caption_attribution_description: Type specimen of Argonauta joanneus (87&#160;mm diameter at widest point)
context_page_description: The argonauts are a group of pelagic octopuses. They are also called paper nautiluses, referring to the paper-thin eggcase that females secrete. This structure lacks the gas-filled chambers present in chambered nautilus shells and is not a true cephalopod shell, but rather an evolutionary innovation unique to the genus Argonauta. It is used as a brood chamber and for trapped surface air to maintain buoyancy. It was once speculated that the argonauts did not manufacture their own eggcases but instead utilized shells abandoned by other organisms, in the manner of hermit crabs. Experiments by pioneering marine biologist Jeanne Villepreux-Power in the early 19th century disproved this hypothesis, as Villepreux-Power was able to successfully rear argonaut young and observe the development of their shells.
  Argonauts are found in tropical and subtropical waters worldwide; they live in the open ocean, i.e. they are pelagic. Like most octopuses, they have a rounded body, eight arms and no fins. However, unlike most octopuses, argonauts live close to the sea surface rather than on the seabed. Argonauta species are characterised by very large eyes and small distal webs.
context_section_description: The genus Argonauta contains up to seven extant species. Several extinct species are also known.
  The valid extant species are:
  Argonauta argo Linnaeus, 1758
  Argonauta hians Lightfoot, 1786
  Argonauta nodosus Lightfoot, 1786
  Argonauta nouryi Lorois, 1852
  While the following taxon is regarded as a nomen dubium:
  Argonauta cornutus Bosc, 1801
  With the species regarded as valid extinct taxa are
  †Argonauta absyrtus Martill & Barker, 2006
  
  †Argonauta itoigawai Tomida, 1983
  
  †Argonauta joanneus Hilber, 1915
  
  †Argonauta oweri Fleming, 1945
  
  †Argonauta sismondai Bellardi, 1872
  
  †Argonauta tokunagai Yokoyama, 1913
  The extinct species Obinautilus awaensis was originally assigned to Argonauta, but has since been transferred to the genus Obinautilus.
caption: Fossilised eggcase of the extinct Miocene species Argonauta joanneus (lateral and keel views)
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