Thursday, 16 February 2017

Pregnant fossil shows bird and crocodile ancestors gave birth to live young

A 245 million-year-old fossil is the first evidence of live births in one of the major groups of animals 
 

Stephan Lautenschlager
Thursday 16 February 2017 00:00 GM

Giving birth to live young is one of the traits we use to distinguish mammals from other animals. But certain kinds of lizards, snakes and amphibians, both living and extinct, also reproduce without laying eggs. In fact, live birth (or viviparity) has evolved more than 100 separate times in non-mammal species throughout history. It seems to have been a common reproductive strategy in particular for extinct aquatic reptiles, such as the fish-like ichthyosaurs, plesiosaurs and mosasaurs that lived at the same time as the dinosaurs.

But one group of animals known as Archosauromorpha, which includes crocodiles, birds and their ancestors the dinosaurs, has never been known to give birth – until now. A recently unearthed fossil, described in a new study by a team of scientists from China, the US, UK and Australia, shows that an ancient species of archosauromorph was giving birth about 245 million years ago.

The newly described specimen belongs to the species Dinocephalosaurus orientalis and was found in sediments from the early Triassic period in Yunnan Province, China. Dinocephalosaurus had a body length of around a metre but with an elongated neck of nearly twice that length. Its skull was relatively small and equipped with needle-like teeth adapted to catch fish and squids.

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