The first fossil evidence of live birth in Mesozoic marine reptiles was reported in the Feb. 12, 2014, issue of the journal Public Library of Science by a team of scientists from China, Italy, and the United States.
Four stone panels extracted from a fossil quarry near Chaohu Lake in Anhui province in China were assembled into a picture from 248 million years ago of the first known live birth in an ichthyosaur genus called Chaohusaurus.
The fossils show one embryo inside the birth canal, one embryo partially emerging from the birth canal, and one embryo that had exited the birth canal. The animals were born head first.
The researchers conclude from the evidence that Chaohusaurus gave birth to live offspring on land instead of in the water as was previously considered to be the most probable birth environment in ichthyosaurs. Chaohusaurus is considered to be the oldest known ichthyosaur.
The evidence presents a picture of live birth in marine reptiles that is 10 million years older than any other known fossil evidence of live birth.
Ichthyosaurs were in majority very large marine animals. The new fossil evidence suggests that during birth these large marine reptiles came onto land or at least came near land in very shallow water to give birth. The behavior may have been a protective measure to prevent predators from eating the newly born ichthyosaurs.