The 120 million-year-old fossil of a 30cm lizard from the Early Cretaceous of China was found pregnant with more than 15 embryos at a level of skeletal development in its body.
Viviparity is rare with reptiles and Naturwissenschaften journal reports only one of five reptiles gives birth to live young.
This is the first time the scientists have documented a general lizard that has produced live young rather than laying eggs.
Researchers from University College London say it was just days from giving birth when it died and was buried during the cretaceous period.
Though Prof Susan Evans from University College London did not find anything unusual with the female lizard initially Sure enough, when I examined it under the microscope, I could see all these little babies.”
This specimen is the oldest pregnant lizard we have seen. It implies physiological adaptations, like adequate blood supply to the embryos and very thin shells - or no shells at all - to allow oxygen supply, evolved very early on,” said Prof Evans.
The fossil was found in the rocks of Jehol Group in north-eastern China, where the fine limestone there has been worn away to gradually reveal hundreds of exquisite specimens of dinosaurs, fish, amphibians, reptiles, birds and mammals, plants and invertebrates.