This extinct group of squid possessed no external shell or conch, as did ammonites, but an internal one resembling an ‘arrow head’. This consists of three parts. The lower end, the 'rostrum', is the strongest and is found most commonly as a fossil. The chambered part (compare Nautilus), the phragmocone, fossilised less easily, and is rarely found in the fossil record. Even rarer are finds in which the proostracum has been preserved. Below this part of the shell the head of the animal was located.

home | back