Zoologists sometimes use the term living fossil loosely. It’s enough for a newly discovered species to belong to a supposedly extinct family or order to earn the name. Much rarer are cases of true living fossils, such as that of the Gulf snapping turtle shown below. Until 1996, zoologists thought the species had died out somewhere between 20,000 and 50,000 years ago. But when herpetologist Scott Thomson of the University of Canberra was asked to identify the shell of an unfamiliar-looking modern turtle found at Lawn Hill Creek in Queensland, he naturally compared it with a snapper fossil that had been found in the same place.
Both the living and fossil turtles, he found, share the same distinctive skeletal structure and unusual shell-plate arrangement. The only difference was the size: at 13 inches the modern shell (a bottom one is shown at left) is 3 inches shorter than the fossil ...
