To track the tortoises and study their habits, biologists attach small VHF transmitters and GPS data loggers to the shell of each tortoise they find. They also paint a unique number on the tortoise’s shell, and file a small notch through one of the keratin scutes at the thin rear edge of the shell, which has a consistency similar to a human fingernail. All this is done after an examination of the tortoise’s health and weight.

Coaxing one of the creatures out of their shelters can be a challenge: if they feel threatened, they oftentimes wedge themselves against the rear wall and ceiling of their miniature caves, which can be yards deep.

“They’re shockingly strong,” said Hillary Hoffman, a herpetologist with the Arizona Game and Fish Department who has been coming to YPG since 2009. “If they don’t want to come out, they’re not coming out.”

A team of scientists, including researchers from the California Academy of Sciences, has reconstructed a detailed "tree of life" for turtles. The specifics of how turtles are related—to one another, to other reptiles, and even to dinosaurs—have been hotly debated for decades. Next generation sequencing technologies in Academy labs have generated unprecedented amounts of genetic information for a thrilling new look at turtles' evolutionary history. These high-tech lab methods revolutionize the way scientists explore species origins and evolutionary relationships, and provide a strong foundation for future looks into Earth's fossil record.

Research results, appearing in Molecular Phylogenetics and Evolution, describe how a new genetic sequencing technique called Ultra Conserved Elements (UCE) reveal turtles' closest relatives across the animal kingdom.

The scary encounter was to celebrate the launch of the zoo’s search for an Irish Junior Conservation Hero.

The new initiative is to help raise awareness about the rapid rate of extinction that is wiping out unique species across the planet.

“If you see one hurt ... it’s best to be cautious and call an expert.

“Also, try and look out for them on the roads. They tend to move slowly across the road when they want to warm up or look for food.”

Lead author Dr Tyler Lyson of Wits University's Evolutionary Studies Institute, the Smithsonian Institution and the Denver Museum of Nature and Science said: "Tortoises have a bizarre body plan and one of the more puzzling aspects to this body plan is the fact that tortoises have locked their ribs up into the iconic tortoise shell. No other animal does this and the likely reason is that ribs play such an important role in breathing in most animals including mammals, birds, crocodilians, and lizards."

Instead tortoises have developed a unique abdominal muscular sling that wraps around their lungs and organs to help them breathe. When and how this mechanism evolved has been unknown.

In snakes and lizards, the external genitals get a little funkier. These reptiles have paired external genitals, even though they only use one at a time during mating.

But all of these genitals spring out of the same embryonic structure, called the cloaca. This structure sends out signals to the cells around it in the embryo, telling them to turn into genitals.

Scientists have wondered why these structures — which are triggered to grow by the same genetic mechanisms during embryonic development, and have the same function in adulthood — develop so differently.

Laophis crotaloides measured between 10 and 13 feet (3 and 4 meters) long and weighed a whopping 57 lbs. (26 kilograms). Today's longest venomous snakes, king cobras (Ophiophagus hannah), can grow to be about 18 feet (5.5 m) long. But at typical weights between 15 and 20 lbs. (6.8 to 9 kg), king cobras are scrawny compared to Laophis.

What makes Laophis even stranger was that it achieved this bulk not in the tropics, where most large reptiles live today, but in seasonal grasslands where winters were cool.