Scuba Adventures by Capt. Ed Spencer

02/15/2026

05/01/2025

05/01/2025

03/09/2024

12/04/2023

This staggering diversity of forms, sculpture and colour is the result of over half a billion years of evolution. Shown here are representatives of all but one living classes of shell-bearing molluscs, namely Gastropoda, Bivalvia, Cephalopoda, Polyplacophora and Scaphopoda*.

Molluscs have existed at least since the Cambrian Period, which started nearly 540 million years ago. This is a time so ancient that all land on Earth was nothing but barren desert – back then there were no animals roaming forests or traversing grassy plains, nor did these habitats exist – in fact, the very first tentative green shoot of the very first plant had yet to emerge out of the ground. The oceans, however, teemed with life to the extent that with the onset of this period came the ‘Cambrian Explosion’ – so named because it brought an incredible richness of new life – even entirely new life forms – into existence. Based on evidence in the fossil record from around the globe, we now know that most of the classes of molluscs depicted here originated in this enigmatic period.

Several molluscan classes, like the ammonites (not shown here), have long gone extinct. Others, especially gastropods, have become incredibly diverse – they are even the only class to have conquered dry land (see bottom right example). We all know land snails are notoriously slow, but it may perhaps still be surprising to learn that it took them at least two hundred million years to get there? Patient creatures, indeed…

* The missing class – the Monoplacophora – is a deep-sea group so elusive it was believed extinct until the 1950s.