The phrase ‘living fossil’ is both widely used and widely argued over. It refers to an ‘archaic’ species that has survived for a long time, whose anatomy harks back to an early stage in the group’s evolutionary tree and has remained unchanged for much of that period.
There are several species that are often referred to as living fossils, including coelacanths, horseshoe crabs, tuataras and nautiloids.
The tree Ginko biloba for example is the only living species of its group and dates back almost 300 million years in the fossil record. However, some species are more problematic – even okapi are considered by some as ‘living fossils’, yet have only existed for 15–20 million years.
The problem with the term ‘living fossil’ is the definition of ‘a long time’ and ‘remained unchanged’. Is a million years a long time, or does it need to be 65 million years? And many species remain largely unchanged for millions of years – even frogs have looked the same for that long – but we don’t call them ‘living fossils’.
Main image: Tuatara, Stephens Island, New Zealand © Getty Images
