Living fossil

Living fossil refers to life forms which have survived with little change for a long time, and which are still around today.

• Horseshoe crabs are a typical case of living fossil. They have changed little in appearance since the Ordovician period, 450 million years ago.

• Crocodilians first appeared 220 million years ago, and are close relatives of the dinosaurs. However, modern crocodiles only date back to the Upper Cretaceous of 84 million years ago.

• Turtles are first known from 215 million years ago, but for some reason they are not often mentioned as living fossils.

• The Tuatara, from New Zealand, is the sole survivor of a whole order of reptiles, the Sphenodontia. 200 million years ago the group (sister to the lizards and snakes) was quite common.

• The Coelacanth is definitely a living fossil. It is the closest link between fish and the first amphibians (408–362 million years ago). The Coelacanth was thought to have been extinct for 80 million years until one was caught alive off the east African coast in 1938. It is therefore also a Lazarus taxon.

• The Ginkgo tree, Ginkgo biloba, is a good example from the world of plants. It is a gymnosperm. It was thought to be long extinct in the wild, but is now known to grow in at least two small areas in China. The first similar fossils date from the Permian period, 270 million years ago.

• Lingula, a brachiopod, is a genus which has lasted since the Ordovician, 488 million years ago. The modern species are almost the same as the first fossils.

Living fossils are not identical to their ancestors, of course. But they lived in the same or similar environments, and their adaptations suggest that their life-style was the same, or very similar.

Figure 11.8: Fossil Lingula (left) and modern Lingula (right).