Fossil Shows Pre-Dino Reptile Giving Birth

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A birth that took place long before the first dinosaurs emerged can be seen now, thanks to a newly unearthed fossil.

The fossil, discovered in China and described in PLOS ONE, freezes in time the moment that an Ichthyosaur gave birth 248 million years ago.

To give you an idea of how long ago that was, the first dinosaurs emerged some 18 million years after this birthing event.

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Ichthyosaurs evolved from terrestrial reptiles and moved to the water. This particular individual and her offspring belonged to the genus Chaohusaurus, the earliest known Mesozoic marine reptile.

“The study reports the oldest vertebrate fossil to capture the ‘moment’ of live-birth, with a baby emerging from the pelvis of its mother,” said author Ryosuke Motani, of the University of California at Davis, in a press release. “The 248-million-year old fossil of an ichthyosaur suggests that live-bearing evolved on land and not in the sea.”

He and his colleagues suspect live birth began on land because the infants were coming out head first, a posture associated with land-dwelling animal births.

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In addition to showing the earliest live birth of an ancient marine reptile, the specimen is also thought to contain the oldest known fossil embryos of Mesozoic marine reptiles.

This mom and her babies are obviously long gone. At least one ichthyosaur species, however, survived until the Early Cretaceous, about 90 million years ago. While it’s long gone too, it shows how successful these animals — as a group — were during their lengthy time on our planet.

Photo: Ryosuke Motani, doi:10.1371/journal.pone.0088640