In an article published yesterday scientists describe an AMAZING fossil: a Chaohusaurus in the midst of live birth. The marine reptile started her labor in the Mesozoic era, millions of years before the first dinosaurs. There are a total of three offspring: one inside the mother, one emerging, and one just born. The research team that made the discovery was led by Ryosuke Motani, a paleontologist at University of California Davis. They explain the importance of the fossil in the abstract of the article published in the journal Plos One:

This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature.

In other words: most marine animals are born tail-first, so the fact that the fossil shows a head-first birth suggests its ancestors were land-dwellers.

More on this remarkable fossil here, here, here and here!

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