Argonauta joanneus is an extinct species of octopus assigned to the genus Argonauta. It was described in 1915 based on fossil material from the Middle Miocene of Austria.Martill, D.M. & M.J. Barker 2006. A paper nautilus (Octopoda, Argonauta) from the Miocene Pakhna Formation of Cyprus. Palaeontology 49(5): 1035-1041. It was found in fine sandy clay.
The type specimen, a fossilised eggcase, measures 84 mm in diameter at its widest point but is only 18 mm thick. The mouth is 48 mm wide.
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