Essential collectibles #5: Turritella gastropods

Dr Neale Monks (UK) Gastropods, or snails, are common fossils thanks to their strong, easily preserved external shells. Quite a few fossil gastropods are traded commercially, including members of the genus Turritella. This particular genus first appears in the fossil record during the mid Cretaceous and includes many species still alive today. If you know where to look, you can even find their shells washed up on beaches around the British Isles, often in considerable numbers, reflecting the success of these animals even today. So while fossil Knightia aren’t valued as rarities, they are extremely informative. The fine details preserved tell us about the anoxic conditions at the bottom of the lake and the fine sediments that quickly smothered the corpse. As herbivores of a sort, these fish occupied a position low down on the food chain meant they could exist in huge numbers, and by dint of that success they were able to support a whole range of predators that either fed directly on them, as with Diplomystus, or further up the food chain. Finally, the fact Knightia can only be found at certain horizons tells us something about the dynamic nature of giant lakes. They might seem unchanging on the human timescale, but on the geological timescale they do change, from being full of life at one point, then hypersaline and dead the next, perhaps even evaporating away completely some time later. The Turritella you’ll find in fossil shops are most commonly Tertiary species, such as the ubiquitous … Read More