A species that has survived over extended periods of geologic time with little or no change to their appearance and biology. One popular living fossil is the coelacanth, a funny-looking fish that was thought to be extinct for over 80 million years until it was hooked off the coast of South Africa in 1938.

Other examples are the tuatara, a lizard-like reptile from New Zealand, and the Ginkgo and Metasequoia, species of trees often found in parks and botanical gardens.

There are a number of other species that are commonly referred to as living fossils. As a result of geographic isolation, most of these species are Australian. This should be considered a partial list, at best, given the rate at which new species are discovered:

• Horseshoe crab
• Ommatidae -- A group beetles now thought to be Austrailia's oldest residents (200 million years)
• Duck-billed platypus
• Spiny ant-eater
• Nightcap oak
• Wollemi pine
• Anaspides
• Nautilus (see also Chambered Nautilus)
• Crocodilians
• Certain sharks, most particularly the megamouth
• Equisetum
• Monkey-tailed tree, Araucaria araucana

While it is great fun to imagine these species as being present during the time of the dinosaurs and even earlier, the term living fossil is considered by many biologists to be sensationalist and perhaps a little dangerous. The problem is the term leads people (particularly creationists) to think that these species are evidence against the theory of evolution. It is important to remember that while these species have remained morphologically unchanged over millions of years, this is not only concordant with by also predicted by the theory of evolution. If a species lives is a successful competitor (example: crocodilians) and has access to refuges during catastrophic events, then the species may not go extict over very long periods of time.