A live birth reptile fossil found recently has scientists dumbfounded, pre-dating the current record by millions of years. It was previously believed that reptiles bore young tail-first, and mammals gave birth to their young head-first. According to National Geographic, the new findings were published in a February 12th edition of the journal, PLOS ONE.

This new revelation is scientific proof of the theory that reptilian births have evolved hundreds of times over the course of history. New research indicates that over the evolutionary trajectory of reproduction, reptiles varied between live birth and egg-laying, the reproductive strategy known as viviparity, before finally becoming a species that gives birth exclusively through egg-laying.

The leader of a study at the University of California, Davis, conducted by prehistoric marine reptile expert Ryosuke Motani, discussed the discovery about the oldest “sea monster” thought to have ever been in existence. The fossils of the mother and her young were of the species ichthyosaur, which belong to the genus Chaohusaurus. The ichthyosaurus is relative to today’s eel, in that its body form was similar to a snake or fish.

The fossil found shows one baby in the birth canal and a second still in the mother’s pelvis, with a third embryo lying nearby. Scientists believe this evidence suggests that the mother was in the midst of a challenging labor.

Ichthyosaurs were the species first to become called “sea monsters,” believed to have been entirely water-birthing reptiles, and the oldest species of their group. The ichthyosaur fossils are considered to be the oldest embryos of a Mesozoic marine reptile to be uncovered in China, making them 248 million years old. The Mesozoic era took place between 252 to 66 million years ago.

Said Motani, “[So] live bearing did not evolve in water as scientists thought. Our assumption was wrong.”

Image via PLOS ONE, plosone.org.