Cirrate shell

Article summary

(73 mm ML). Cirrate octopuses possess a well-developed internal shell that supports their muscular swimming fins. This is in contrast to the more familiar, finless, incirrate octopuses, in which the shell remnant is either present as a pair of stylets or absent altogether. The cirrate shell is quite unlike that of any other living cephalopod group and has its own dedicated set of descriptive terms. It is usually roughly arch- or saddle-shaped and is rather soft, being similar in consistency to cartilage. Each of the eight extant cirrate genera is characterised by a distinct shell morphology outlined below (below taxonomy updated per WoRMS): *Superfamily Cirroteuthoidea **Cirroteuthidae ***Cirroteuthis — saddle-shaped, with large wings ***Cirrothauma — butterfly-shaped **Stauroteuthidae ***Stauroteuthis — U-shaped *Superfamily Opisthoteuthoidea **Opisthoteuthidae ***Opisthoteuthis (also Exsuperoteuthis & Insigniteuthis)— U-shaped, lateral wings usually tapering to fine points but termination complex in certain species **Cirroctopodidae ***Cirroctopus — V-shaped, lateral wings tapering to fine points **Grimpoteuthidae ***Grimpoteuthis — U-shaped, lateral wings ends expanded in a broad lobe (with offset spike present or absent). ***Luteuthis — W-shaped, lateral wings ends expanded (with offset spike present).…

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