Cephalopds (Phylum Mollusca)

© Craven & Pendle Geological Society

Coal Measure Ammonoid

Gastrioceras listeri

The Cephalopods (typically goniatites in Carboniferous rocks and Ammonites in Mesozoic times) are highly developed molluscs.  They are characterised by a well-developed sensory system and a large brain by invertebrate standards.  Squids, cuttlefish and octopuses are living examples of this class.  Even Gastrioceras has a living relative in Nautilus.

Gastrioceras has a coiled external shell.  The shell is divided into chambers, one of which contains the living soft parts of the animal, whilst the others are frequently filled with gas (provides the buoyancy).  A tube called the siphuncle connects the chambers.  The line of contact between the septum and the shell is called the suture line.  It is this line that is used to categorise the various animals into genus and species.  These are important fossils as they have been used to zone the strata Upper Carboniferous times.

Fossiliferous Coal Bobber

Aviculopecten plicatus