This 248 million-year-old fossil is incredible for two reasons. First, it shows the tragic moment an Ichthyosaur died giving birth. Second, it's the oldest evidence of a live reptilian birth — about 10 million years older than previous samples.

The fossil is that of a Chaohusaurus, a giant marine reptile that looked like a cross between a dolphin and a lizard, but with flippers and no dorsal fin. Ichthyosaurs evolved from terrestrial reptiles and adapted to aquatic life.


As you can clearly see, the baby's head is emerging from the mother's pelvis head first.

The researchers say that at least two other offspring were involved, including one still inside the mother, and the other laying beside her.

The fossil indicates that live, head-first births in ancient reptiles evolved much earlier than previously thought — and they evolved this trait while they were still on land.


"Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity [producing living young, and not eggs], in contrast to the traditional view," write the authors in the study.

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Read the entire study at PLoS One: "Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils."

Image: Ryosuke Motani

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