Common Squid - Loligo vulgaris

Common Squid - Loligo vulgaris, Cephalopod mollusc belonging to the Decapod order; very tapering body ending in a pair of triangular, lateral fins. Small head with 8 arms and two extendible tentacles with widened extremeties. Reddish. Found in coastal waters from 10-20 metres to over 200 metres. Maximum size 40 centimetres.

Squid have differentiated from their ancestral molluscs in such a way that the body plan has been condensed antero-posteriorly and extended dorso-ventrally. What before may have been the foot of the ancestor is now modified into a complex set of tentacles and highly developed sense organs, including advanced eyes similar to those of vertebrates.
The shell of the ancestor has been lost, with only an internal gladius, or pen, remaining. The pen is a feather-shaped internal structure that supports the mantle of squid and serves as a site for muscle attachment. It is made of a chitin-like substance.

Common Squid