The Oldest pregnant lizard fossil discovered
The lizard in this case has been identified as Yabeinosaurus which scientists believe to be similar to the gecko. Evans did not pay much attention to the fossil when it was first discovered but Yuan Wang from the Chinese Academy of Sciences examined the fossil and discovered 15 tiny fossilized embryos.
The embryos were almost fully developed and the researchers believe that the foot-long mother died only a few days before she would have given birth.
This discovery reveals that some lizards were giving birth to live young in the Early Cretaceous period. Previous fossils have shown that some marine lizards gave birth to live young but this is the first primarily land lizard to be discovered.
“We previously thought that lizards adapted to live birth after mammals, but now it looks like it happened at roughly the same kind of time. This specimen is the oldest we have seen, which 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 Professor Susan Evans.
For lizards the added weight throughout the gestational period can limit their movement and ability to flee from predators. This lizard was believed to have lived on a river bank or somewhere close to water where it was able to flee to water in order to move easier.
"We do know that this lizard lived near to water and we think it likely that they could swim even though they primarily lived on land. This would make sense as a pregnant lizard would be less constrained by carrying offspring – she’d be able to escape into water if a hungry dinosaur came along!” she added.
More information: A gravid lizard from the Cretaceous of China and the early history of squamate viviparity, by Yuan Wang and Susan E. Evans, Naturwissenschaft, DOI:10.1007/s00114-011-0820-1
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| The pregnant gravid female Yabeinosaurus fossil. Credit: Susan Evans/UCL |
A new paper published in Naturwissenschaft reveals a fossil from 120 million years ago that proves that some lizards were not laying eggs but rather giving birth to live young.
The fossil was discovered by Susan Evans, a professor from the University College London Department of Cell and Developmental Biology, in the Jehol region of Northeast China. This area has revealed hundreds of dinosaur, amphibian, reptile, fish, bird, mammal, invertebrate and plant fossils. The lizard in this case has been identified as Yabeinosaurus which scientists believe to be similar to the gecko. Evans did not pay much attention to the fossil when it was first discovered but Yuan Wang from the Chinese Academy of Sciences examined the fossil and discovered 15 tiny fossilized embryos.
The embryos were almost fully developed and the researchers believe that the foot-long mother died only a few days before she would have given birth.
This discovery reveals that some lizards were giving birth to live young in the Early Cretaceous period. Previous fossils have shown that some marine lizards gave birth to live young but this is the first primarily land lizard to be discovered.
“We previously thought that lizards adapted to live birth after mammals, but now it looks like it happened at roughly the same kind of time. This specimen is the oldest we have seen, which 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 Professor Susan Evans.
For lizards the added weight throughout the gestational period can limit their movement and ability to flee from predators. This lizard was believed to have lived on a river bank or somewhere close to water where it was able to flee to water in order to move easier.
"We do know that this lizard lived near to water and we think it likely that they could swim even though they primarily lived on land. This would make sense as a pregnant lizard would be less constrained by carrying offspring – she’d be able to escape into water if a hungry dinosaur came along!” she added.
More information: A gravid lizard from the Cretaceous of China and the early history of squamate viviparity, by Yuan Wang and Susan E. Evans, Naturwissenschaft, DOI:10.1007/s00114-011-0820-1
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