When a lizard flees a predator, it may leave its wriggling tail behind as it escapes. This defense mechanism is well known among modern lizards, but until now no direct fossil evidence had been found showing that it was already in use tens of millions of years ago. Researchers at Tel Aviv University have now discovered a detached lizard tail preserved in a 99 million-year-old piece of amber from northern Myanmar, providing the oldest direct evidence of the phenomenon ever found.
The study was led by Dolev Fabrikant, a doctoral student at Tel Aviv University's School of Environmental Sciences, under the supervision of Dr. Leonidas-Romanos Davranoglou of the School of Zoology and the Steinhardt Museum of Natural History. The research was conducted in collaboration with scientists from the University of Athens and Israel's Volcani Institute. The findings were published in the journal Palaeontologia Electronica.
According to the researchers, earlier fossils had provided clues that ancient reptiles were capable of shedding their tails, including fracture planes in vertebrae and evidence of regenerated tails. However, those findings did not prove that the tails had actually detached as part of a defense mechanism. The newly discovered fossil provides direct evidence: the point where the tail separated from the body has been preserved, complete with features that allow researchers to examine how the detachment occurred.
For years, no one recognized the significance of the piece of amber. What initially appeared to be a tiny twig or an insect fragment caught Fabrikant's attention. "When I looked more closely, I realized that what looked like a twig was covered in tiny scales," he recalled. "It was a lizard's tail."
When Fabrikant told his supervisor about the discovery, the reaction was immediate.
"I almost jumped out of my chair," Davranoglou said. "I immediately realized that this tiny fossil could open an extraordinary window into the past and help us understand the history of one of the most common survival strategies among reptiles. Until now, we could only speculate whether these ancient lizards were capable of shedding their tails. Now we have direct evidence that one of them actually did."
The lizard's tail inside the amber on the left
(Photo: Tel Aviv University)
The hallmarks of an eagle's tail
(Photo: Tel Aviv University)
The amber's cloudiness made it difficult to examine the fossil in detail. In addition to conventional microscopy, the researchers therefore used X-ray micro-computed tomography, or micro-CT scanning, at the Volcani Institute.
"Micro-CT technology takes X-ray images from multiple angles and combines them into a three-dimensional reconstruction of the specimen. It allowed us to examine structures hidden inside the amber without having to cut open this unique specimen," explained Dr. Ahmed Nasser, head of the institute's Inter-Institutional Analytical Unit.
The researchers identified a ring-shaped tissue structure at the detached end of the tail, similar to a feature formed when modern lizards deliberately shed their tails. The separation point was also relatively clean and symmetrical, lacking the tearing or twisting marks typically associated with accidental injury.
Despite the fossil's exceptional preservation, the tail alone does not provide enough information to determine precisely which group of lizards the animal belonged to.
From right to left: Dr. Leonidas-Romanos Davarnoglu, Dolev Fabrikant and Dr. Ahmed Nasser
(Photo: Tel Aviv University)
Apostolos Christopoulos, a doctoral student at the University of Athens
(Photo: The National and Kapodistrian University of Athens)
"Although we can say with certainty that it was a lizard, we lack additional skeletal features, such as the skull, that would allow for a more definitive identification. It may have been related to a group that includes modern wall lizards or, alternatively, slow worms and monitor lizards," said Apostolos Christopoulos, a doctoral student at the University of Athens.
The researchers also do not know what caused the lizard to shed its tail. It may have become trapped in sticky resin and detached its tail to escape, or it may have shed the tail during an attempted predatory attack, with the detached appendage subsequently falling into the resin.
"We also don't know what happened to this lizard or whether it actually managed to escape. But the tail it left behind tells us that the defense mechanism familiar to us from its modern relatives was already operating in the age of the dinosaurs," the researchers reported. "Inside a piece of ancient resin small enough to rest on a fingertip lies evidence of a survival strategy that can still be seen today in gardens and on sunlit walls."