Living fossils

Lineages whose body plan has changed remarkably little over very long spans of time.

• Atlantic Horseshoe CrabLimulus polyphemus
• West Indian Ocean CoelacanthLatimeria chalumnae
• Nautilus pompilius
• Lingulid LampshellLingula anatina
• TuataraSphenodon punctatus
• Neoceratodus forsteri

About this list

The phrase is Darwin's and it is not quite right. None of these animals stopped evolving; their genomes have changed at ordinary rates, and living species are not identical to their fossil relatives. What is conserved is the external body plan, usually in lineages that found a stable habitat and stayed in it.

The coelacanth is the emblematic case: known only as Cretaceous fossils until a trawler landed one off South Africa in 1938.