18:21 15 February 2017
Scientists have uncovered the first evidence of live births in the group of animals that includes birds, dinosaurs and crocodiles. The finding is significant as all examples of this group, know as the Archosauromorpha, lay eggs.
A fossil remains of a very long-necked marine reptile discovered in China revealed it was carrying an embryo. The discovery proved that there is no fundamental biological barrier to live birth exists in this group and as such, palaeontologists would be “looking very closely” at other fossils.
The mode of reproduction in Dinocephalosaurus also points to how the sex of its offspring was determined.
Co-author Prof Chris Organ, from Montana State University, added: "Some reptiles today, such as crocodiles, determine the sex of their offspring by the temperature inside the nest.
"We identified that Dinocephalosaurus, a distant ancestor of crocodiles, determined the sex of its babies genetically, like mammals and birds."
Co-author Prof Mike Benton, from the University of Bristol, explained: "This combination of live birth and genotypic sex determination seems to have been necessary for animals such as Dinocephalosaurus to become aquatic.
"It's great to see such an important step forward in our understanding of the evolution of a major group coming from a chance fossil find in a Chinese field."
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