Fossil of pregnant lizard discovered


Share post:

A 120-million-year-old fossil is the oldest pregnant lizard ever discovered, according to scientists. The fossil, found in China, is a very complete 30cm (12in) lizard with more than a dozen embryos in its body. 

The lizard was just days from giving birth when it died and was buried [Credit: BBC]

Researchers from University College London, who studied the fossil, say it was just days from giving birth when it died and was buried during the Cretaceous period. The team reports the findings in the journal Naturwissenschaften.  

The fossil is especially interesting to scientists because it is a reptile that produced live young rather than laying eggs. Only 20% of living lizards and snakes produce live young, and this shows it is an ancient, if unusual, trait. 

“I didn’t think much of the fossil when I first saw it,” said Prof Susan Evans, joint lead author of the paper, from University College London. 

But when her colleague, Yuan Wang, from the Chinese Academy of Sciences, examined the fossil he spotted the tiny remains of at least 15 almost fully developed embryos inside it. 

“Sure enough, when I examined it under the microscope, I could see all these little babies,” Prof Evans recalled.  

The fossil is so well preserved that the minuscule teeth of the developing young are visible on very close inspection. 

“This specimen is the oldest pregnant lizard we have seen,” said Prof Evans. 

“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.” 

The heads of at least 15 lizard embryos are visible inside the body of the fossil [Credit: BBC]

Up until now the fossil records only contained examples of marine lizards giving birth to live young. 

Scientists thought that, in extinct reptiles, live birth was restricted to aquatic species, such as marine ichthyosaurs. These creatures would have been able to move through water with relative ease, even when heavily pregnant.  

Prof Evans said: “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.” 

The fossil comes from world famous rocks of the Jehol Group in north-eastern China, where the fine limestone there has been worn away to gradually reveal hundreds of exquisite specimens of dinosaurs, but also fish, amphibians, reptiles, birds and mammals, plants and invertebrates. 

The mother lizard has been identified as a specimen of Yabeinosaurus, a large, slow-growing and relatively primitive lizard.  

Author: Victoria Gill | Source: BBC News Website [July 21, 2011]



Related articles

Primitive birds shared dinosaurs’ fate

A new study puts an end to the longstanding debate about how archaic birds went extinct, suggesting they...

Butterflies’ diet impacts evolution of traits

Why do some organisms within a single species have many offspring, while others have relatively few? A new...

New progress of research on fossil Equus

Stenonid horse is the earliest Equus in Eurasia. The first occurrence of stenonid horse in Eurasia was regarded...

The first crocodile ancestors

Did you know that birds and crocodiles are practically cousins? Around 230 million years ago, you wouldn't have...

New study shows three abrupt pulses of CO2 during last deglaciation

A new study shows that the rise of atmospheric carbon dioxide that contributed to the end of the...

Neo-Assyrian clay tokens unearthed in SE Turkey

Prehistoric ‘bookkeeping’ continued long after invention of writing. An archaeological dig in southeast Turkey has uncovered a large...

Elaborate Roman copper mining operation uncovered in Spain

Archaeologists working in Southern Spain, in the ancient city of Munigua, have discovered an elaborate copper mining operation...

Reducing numbers of one carnivore species indirectly leads to extinction of others

Previous studies have shown that carnivores can have indirect positive effects on each other, which means that when...