Fossil gives 1st evidence of live birth in ancient reptile thought to lay only eggs

Scientists have found a 250-million-year-old fossil with an embryo inside the mother, evidence of live birth bya group of animals that were thought to reproduce only by laying eggs.

The Dinocephalosaurusbelongs to a group called Archosauromorpha, which includesdinosaurs as well asbirds and crocodiles alive today. The long-necked marine animal lived in shallow waters near south China during the Middle Triassic Period.

It was believed that this group only laid eggs. However, this new discovery, announced Tuesday in the journal Nature Communications,"pushes back evidence for reproductive biology by about 50 million years," Jun Liu from the University of Technology in China said in a statement.

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It was unclear at first whether the paleontologists had found an embryo or the reptile's last meal. Further study revealed the valuable fossil could change our thinking about dinosaurs and their distant descendants.

Researchers ruled out the embryo as a meal because it was found in the rib cage facing forward, whereasprey would be eaten head first. As well the animal and embryo werethe same species.

The gender of a crocodile's offspring is influenced by environmental factors. However, genetics was the prime determinant of the Dinocephalosaurus, as is found in birds and mammals.