The cracks in the middle of many tail vertebrae of a reptile that lived 289 million years ago allowed the animal to escape from the grasp of its predator. The Captorhinus detached their tail when caught in a life-threatening situation.

The predator then is left with nothing but a wiggling tail for its next meals, instead of a two-kilogram reptile. It is the oldest known example of such type of defense mechanism, according to the study published in the March 5 issue of Scientific Journals, an open source journal.

Distant relatives of today's reptiles

Professor Robert Reisz, the team leader, said that the Captorhinus was smaller than the predators during the time. The reptile was abundant in terrestrial communities during the Early Permian period. It is a distant relative of today's reptiles, Science Daily reported.

The outstanding feature of the animal was its breakable tail vertebrae, Aaron LeBlanc, a PhD student, said. He explained that the cracks acted like perforated lines between two paper towel sheets. It allowed the vertebrae to break in half along the planes of weakness. It also gave the reptile a chance to escape relatively unharmed from its predator, Reisz said.

The Captorhinus was the most common reptile during its time. The escape strategy could be the key to the success of the species that by the end of the Permian period 251 million years ago, the reptile had dispersed across the Pangaea, the ancient supercontinent.

When the Captorhinus died out, the trait disappeared from the fossil record. But it re-evolved in lizards only 70 million years ago. The researchers were able to study more than 70 tail vertebrae of adult and juvenile reptiles at the treasure trove of fossils at the cave deposits near Richards Spur in Oklahoma. They found partial tail skeletons with splits that ran through the animal's vertebrae.

Naturally formed vertebrae

The researchers compared the skeletons of the Captorhinus to its reptilian relatives. They found that the ability to free from its tail is restricted to the family of reptiles in the Permian period, UPI reported. By using different paleontological and histological techniques, the scientists found that the cracks were features that formed naturally as the vertebrae were developing.

The well-formed cracks were observed in young captorhinus, while the vertebrae of the adults tended to fuse up. The researchers noted that it made sense since the young reptile was at greater risk from predators and the animal needed the ability to defend itself.

Important reptiles

In the book "The Paleozoic Era: Diversification of Plant and Animal Life," the authors noted that while a few primitive and generalized reptile fossils were found in Carboniferous deposits, the Permian reptile fossils were common in certain locations. Included are the captorhinomorphs, protosaurs, and aquatic reptiles that are the ancestors to archosaurs such as dinosaurs, crocodiles, and birds.

The captorhinomorphs were observed to be more common in the Lower Permian beds of North America and Europe. The species was built massively and was large for its day because it reached lengths of two to three meters. But the species was less common in Upper Permian beds, with only one small group that survived into the Triassic Period.

During the latter part of the Permian period, the greatest mass extinction episode in Earth's history happened. In that era, the shallow warm-water marine invertebrates showed the most protracted and greatest extinction. In the middle part of the Middle Permian Epoch, the extinction of the invertebrate faunas reduced the number of different genera by 12 percent to 70 percent at the beginning of the Capitation age.

Representatives of captorhinomorphs

Based on fossils in Permian rocks of North America, the Captorhinus had slender limbs, while the skull was only about seven centimeters long. It resembled the modern lizard. In form, the Captorhinus was representative of the captorhinomorphs, which is a group of early reptiles with nearly solid skulls with no openings for the attachment of jaw muscles.

Reptiles with more advanced skills and stronger jaws for biting and chewing food eventually succeeded the captorhinomorphs. But there was one small group of captohinomorphs that persisted into the Triassic Period 251 million to 200 million years ago before it became extinct.

Tail grows back

Huffington Post reported that the ability to grow back the lost tail was observed in lizards. Researchers pinpointed the genes responsible for tail regenerations which could possibly yield important clues on how to regenerate limbs in humans.

When the scientists examined about 23,000 genes found in samples of sliced-up tails of the green anole lizards, they discovered at least 326 genes in specific spots along each tail that were turned on during regeneration. It suggested that the lizard DNA has a genetic recipe for regeneration.

They expected all of the regeneration to be focused at the tip of the growing tail, but the researchers found that the cells are instead dividing into distinct pockets, including muscle, cartilage, spinal cord, and the skin all throughout the tail, Dr. Kenro Kusumi, a professor of life sciences at Arizona State University, said. It takes lizards more than 60 days to regenerate a functional tail, Elizabeth Hutchins, a graduate student at ASU said.

[researchpaper 리서치페이퍼= Vittorio Hernandez 기자]