Living Fossils

The Wami River in Tanzania carries vast amounts sediment down to the sea, much of it deposited to the north of the river's mouth to form wide sandy beaches and underwater banks which are exposed at low tide. The coast here is unlike the usual East African coast to which I was accustomed, where a coral reef protects a lagoon, so it has an ecosystem of its own which includes....

....these sea urchins, often called 'sand dollars', which work their way through the sand a few centimetres below its surface. When, on our first visit to the lodge at Saadani, I found the first one I couldn't believe my eyes: the only sand dollars I had seen were fossils from the Jurassic.

The beach continued to surprise. Another of the inhabitants of the sands is this snail, the likes of which, again, I had only seen as fossils: I knew it by the broad name of 'Turritella'.

One of the branches of geology that I particularly enjoyed was palaeontology, the study of fossils. So many of the fossils I found had no living relative so one had to infer the environment in which they lived using evidence such as the sediment in which they were preserved. Inevitably, then, I recall being very excited when I came across these old friends, very alive and ploughing their way through the sands of a beach to the north of Dar-es-Salaam.