What is the oldest animal species still alive?
Sponges are among the oldest animal lineages still alive, with origins over 600 million years ago. Horseshoe crabs, coelacanths and tuatara are famous living fossils that have changed little over hundreds of millions of years.
Sponges are simple animals without organs or nervous systems, living attached to the seafloor. Fossil and chemical evidence suggest their ancestors existed more than 600 million years ago. Some scientists think comb jellies may be even older. Of course, today's species are not identical to ancient ones, but these groups have remained similar for a very long time.
Horseshoe crabs have existed for about 445 million years, surviving several mass extinctions. Coelacanths, fish once thought to have died out with the dinosaurs, were rediscovered alive off South Africa in 1938. The tuatara of New Zealand is the last survivor of a reptile group that thrived about 200 million years ago.
Ancient creatures
Other ancient groups include jellyfish, nautiluses and some sharks, whose ancestors appeared more than 400 million years ago. Crocodiles' ancestors lived alongside the dinosaurs.
Did You Know?
Horseshoe crab blood is blue because it contains copper, and it is used to test medicines and vaccines for bacterial contamination.