A team of scientists from China discovered the fossil of an ancestor of the crocodile that hid an unexpected surprise. For the first time, this fossil brings evidence of live births in animals that were previously thought to only lay eggs.
The crocodile ancestor which they discovered is about 250 million years old. Inside the fossil, they found an embryo, which suggest that this species gave live births. The fossil belongs to a distant ancestor of the crocodile which used to dwell in the shallow seas of Southern China during the Middle Triassic.
Live birth is common in mammals, where the embryo can develop by nourishing from the mother’s placenta. It can also be seen in lizards and snakes, where babies may hatch inside the mother and emerge without being covered in the shell of an egg. Crocodiles usually only laid eggs, until recently.
The researchers from Hefei University of Technology in China were the ones that discovered the fossil. They identified it as belonging to a Dinocephalosaurus, a long-necked animal that lived in Southern China. Inside the ribcage of the mother, they found an embryo which was facing forwards.
The placement of the embryo suggests the fact that it was not eaten, since animals are swallowed head first by the predator and thus would be facing backwards. More evidence that the fossil was the mother of the embryo is the fact that the little being is of the same species as the big fossil.
Professor Jun Liu is the leader of the study. He declared himself excited of their discovery and of the embryo that had the potential to be evidence for live births among reptiles. They made the discovery several years ago but, after close analysis, they were now able to assure the fact that the embryo was not a prey.
This is the first case of live birth in the wide group of species, including birds, crocodilians, and dinosaurs. Until now, there was no information available on the reproduction of this group. For example, they determined that Dinocephalosaurus determined the sex of their babies genetically, and not from the temperature of the nest, as it was the case with some reptiles today.
This discovery is important since it brings highlights on the way in which ancient reptiles reproduced and also offers valuable information on the evolution of reptiles and crocodilians.
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