From Wildlife Extra:
World’s oldest species resurfaces in Scotland
August 2008. Not everyone is unhappy about the dire August weather in the UK; it seems the recent downpours have provided ideal conditions for the re-emergence of near-extinct Tadpole Shrimps on the Wildfowl & Wetlands Trust’s Caerlaverock reserve in Scotland.
The Tadpole Shrimp (Triops cancriformis) is a living fossil, thought to be the oldest living creature on the planet. Resembling a small Horsehoe Crab, it has been recorded from at least 220 million years ago in the Triassic period, even before dinosaurs roamed the earth, and may be as much as 300 million years old. The species was first discovered in Britain in the south west Scotland in 1907 just west of Caerlaverock on Preston Merse in Kirkcudbrightshire. However, it was thought to have become extinct in Scotland when the ponds were lost to the sea in 1948.
In Britain, it is currently only known in a single pool in the New Forest. However Tadpole Shrimps were first discovered at WWT Caerlaverock four years ago, again, after a particularly wet August. Back then, in late summer 2004, WWT researcher Dr Larry Griffin found a colony in a small pool on the saltmarsh of the reserve while carrying out a late survey for Natterjack Toads.
Australia’s only shield shrimp: here.
Horseshoe crabs: here.