Sunday 2 December 2018

HOLCOPHYLLOCERAS

Amazing suturing on this lovely ammonite, Holcophylloceras mediterraneum, (Neumayr 1871) from Late Jurassic (Oxfordian) deposits near Sokoja, Madagasgar.

The shells had many chambers divided by walls called septa. The chambers were connected by a tube called a siphuncle which allowed for the control of buoyancy with the hollow inner chambers of the shell acting as air tanks to help them float.

They were a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids — octopuses, squid, and cuttlefish) then they are to shelled nautiloids such as the living Nautilus species.

We can see the edges of this specimen's shell where it would have continued out to the last chamber, the body-chamber, where the ammonite lived. Picture a squid or octopus, now add a shell and a ton of water. That's him!