LIVING FOSSILS

FOR SOME CREATURES ALIVE TODAY TIME HAS ALMOST STOOD STILL. MEET THE 'LIVING FOSSILS' THAT GIVE US A GLIMPSE INTO LIFE IN THE DISTANT PAST

- WILL NEWTON

No individual species alive today was around during the age of the dinosaurs, between 24666 million years ago. But there are several groups of species currently roaming the Earth who can trace their roots back to ancient ancestors that would have looked remarkably similar.

For these organisms - so-called 'living fossils' - time has almost stood still. That's not to say they're entirely unchanged, however; their DNA is distinct and has been put through the evolutionary wringer many times.

These living fossils give us a glimpse into what life was like millions of years ago. They also show us just how resilient some groups have been to calamitous, prehistoric events that have consigned others - such as the dinosaurs, for example - to extinction.

CROCODILIANS

There are more than two dozen species of crocodilians alive today, including true crocodiles, alligators, caimans and gharials. These extant crocodilians share a common ancestor that lived alongside the dinosaurs in the Late Cretaceous, about 80 million years ago (Mya).This common ancestor looked a lot like today's crocodilians and, like them, spent most of its time hanging out at the water's edge, soaking up the sun and waiting for unsuspecting prey to enter its domain.

While they may look unchanged after nearly 80 million years, today's crocodilians are a far cry from their distant ancestors, which first appeared in the Late Triassic, around 235 Mya. These extinct, crocodilian relatives were considerably more diverse than their modern descendants. Some, like Litargosuchus, were built like whippets and pursued small prey on land much like wolves, while others, such as Sarcosuchus, (illustrated above left) grew to colossal lengths of up to 12m (almost 40ft) and snatched elephant-sized dinosaurs from riverbanks.