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Dinosaur birth can be dangerous (Image: Ryosuke Montani)

Something went terribly wrong as this ancient ichthyosaur was giving birth, and she died along with her offspring

Discovered: South Majiashan, China, 2011
Age: 248 million years
Location: Anhui Geological Museum, China

Birth is a dangerous process, and for this very ancient ichthyosaur mother it went terribly wrong. She was carrying at least three offspring. One was found under the mother’s body. The third was still inside her, waiting to be born. And the second was half-way out of the birth canal, making this fossil unique.

Only part of the mother was found because the team that collected the rock in 2011 had no idea it contained ichthyosaurs – they were after a predatory fish. The ichthyosaurs were discovered only in 2012 when the fish fossil was being prepared in the lab and by this time it was too late to recover the rest of the mother, says team member Ryosuke Motani of the University of California at Davis. But they found other fossils of the same species, Chaohusaurus, which were around a metre long.

There is another fossil of an ichthyosaur that might also have been giving birth. But in this case the embryo is almost entirely outside the body and it has been suggested it was expelled by gases as the mother, a Stenopterygius, decomposed on the seabed. For the Chaohusaurus, Motani thinks this scenario is unlikely since it had already given birth to one offspring and the second was only halfway out (see diagram).FIG-mg30091201.jpg

The fossil is extraordinary for other reasons, too. Chaohusaurus is the earliest known ichthyosaur, and this mother at least was giving birth head first. Yet air-breathing animals that live in water, from later ichthyosaurs to modern dolphins and whales, almost always give birth tail first, to reduce the chances of their offspring drowning.

Because all the offspring were oriented head first, and lacked room to reorient themselves, Montani doesn’t think this was an accidental breech birth (). Instead, he thinks the unknown ancestors of ichthyosaurs had evolved live birth on land before taking to the water, and so gave birth head-first like most land animals. Chaohusaurus still retained that trait, but later ichthyosaurs evolved to give birth tail-first.

Read more: “Stunning fossils: The seven most amazing ever found“