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A few differences between cuttlefish and squid

A few weeks back we shone the light on the Common Cuttlefish which gave rise to questions relating to the differences between cuttlefish and squid. Today we will share some of the differences.
Cuttlefish are members of the Sepiida genus whilst squid are member of the Teuthida genus.
Possibly the most recognisable difference between squid and cuttlefish is the shape. Squid are much more elongated and cylindrical, while cuttlefish are more flattened and oval-shaped.
Another important difference between squid and cuttlefish is the shape of their internal shells. A squid’s is thin, flat, transparent and made of cartilage whilst the internal shell of a cuttlefish is spoon-shaped and primarily made of calcium carbonate.
Both squid and cuttlefish have two main tentacles and eight arms, however the arms and tentacles of squid are noticeably longer than that of cuttlefish.
If you are able to see their eyes closeup, you will notice that the cuttlefish has W or M shaped pupils whilst the squid has rounded pupils.
The cuttlefish female watches over her eggs for a month or two until they hatch whilst the squid merely leaves her fertilized eggs alone on the seafloor and goes on with her life.
The cuttlefish does not have the two triangular muscular skinny flaps on its sides which are present in squid.
Thank you to Don Hunter for the incredible shoal of squid image