First Live Birth Evidence Discovered In Animals Previously Thought To Lay Eggs

Posted: Feb 15 2017, 6:17am CST | by , in News | Latest Science News

First Live Birth Evidence Discovered in Animals Previously Thought to Lay Eggs
This is a reconstruction of Dinocephalosaurus showing the rough position of the embryo within the mother. Credit: Dinghua Yang
  • This Ancient Reptile didn’t Lay Eggs but gave Birth to Live Young

Evidence has been found that an ancient reptile didn’t lay eggs but instead gave birth to live young.

The proof is here that a very ancient reptile which was thought to lay eggs actually gave birth to live young. The group of experts studied the remains of this age-old reptile in China.

The remains consisted of a 250 million year old fossil of a mother reptile with her embryo inside her body. While live birth is a common phenomenon among mammals, it is hard to come by in reptiles which normally lay eggs.

In mammals, the mother animal has a placenta by means of which she fulfills the nutritional needs of the young. Some lizards and snakes also have their young ones hatch within the bodies of the mothers and then come out from the birth orifices.

As for modern-day crocodiles and avian species, they just lay eggs. These reptiles are part of the larger group known as Archosauromorpha. The phenomenon of laying eggs is a primitive reflex normally seen in amphibians and fish.

Coming back to the topic under discussion, the ancient reptile had a lengthy neck. Termed Dinocephalosaurus, it thrived in the waterways of Southern China during the Triassic Period.

This creature ate fish by craning its long neck here and there. The fossil remains showed the embryo within the ribcage of the mother. It was pointing towards the front.

The doubts about the creature within the belly being prey were allayed after it was noted down that in that case it would be facing backwards.

Also the baby creature resembled the mother so it could not have been a prey source. This finding has been interesting in that it has upturned many previously held theories.

Lead study author, Professor Jun Liu from Hefei University of Technology in China, said: "We were so excited when we first saw this embryonic specimen several years ago but we were not sure if the embryonic specimen is the last lunch of the mother or its unborn baby.

"Upon further preparation and closer inspection, we realised that something unusual has been discovered.

"Further evolutionary analysis reveals the first case of live birth in such a wide group containing birds, crocodilians, dinosaurs and pterosaurs among others, and pushes back evidence of reproductive biology in the group by 50 million years.

"Information on reproductive biology of archosauromorphs before the Jurassic period was not available until our discovery, despite a history of 260 million years."

This was the first case of live birth in ancient reptiles which include within their purview: avians, crocodiles, dinosaurs and pterosaurs. This time in prehistory goes back to the days befor the Jurassic Period began.

Sex precision also began with this live birth phenomenon in early reptiles. Even today, crocodiles determine the gender of their progeny by the temperature of the nest.

Professor Chris Organ, another author from Montana State University, added: "Some reptiles today, such as crocodiles, determine the sex of their offspring by the temperature inside the nest.

"We identified that Dinocephalosaurus, a distant ancestor of crocodiles, determined the sex of its babies genetically, like mammals and birds."

This study thus happens to be a game changer that has transformed our understanding of reproductive system evolution. The evolutionary history of these reptiles shows anomalies and quirks via this research finding. Mainly, the evidence comes from the fossil relics of this creature that was extant so long ago.

Professor Mike Benton, another co-author from the School of Earth Sciences at the University of Bristol, said: "The analysis of the evolutionary position of the new specimens shows there is no fundamental reason why archosauromorphs could not have evolved live birth.

"This combination of live birth and genotypic sex determination seems to have been necessary for animals such as Dinocephalosaurus to become aquatic. It's great to see such an important step forward in our understanding of the evolution of a major group coming from a chance fossil find in a Chinese field."

This new study got published in the journal Nature Communications.

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<a href="/latest_stories/all/all/20" rel="author">Sumayah Aamir</a>
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