An international team of researchers have found a dinosaur that gives live birth instead of laying eggs like other dinosaur types. The fossil was discovered in China and date back 250 million years ago.
The dinosaur is a long-necked marine animal. It is called Dinocephalosaurus , which is part of the group archosauromorph, and lived in the middle of the Middle Triassic Period in the shallow seas of South China.
Further analysis of the Dinocephalosaurus fossil, which was found perfectly well-preserved, show that it was a fish-eater and turned its long neck from side to side to catch food. No similar fossils can be found in Australia.
This dinosaur provides the first evidence for live birth among dinosaurs, which were only known to have laid eggs. Meanwhile, live birth is commonly an ability among mammals, which is made possible by their placenta to nourish the developing embryo, co-author Professor Jonathan Aitchison, who is also the head of The University of Queensland’s School of Earth and Environmental Sciences.
However, live birth can also be found in lizards and snakes. The babies hatch inside their mother and come out without an egg.
“We were not sure if the embryonic specimen was the mother’s last lunch or its unborn baby,” adds lead author Professor Jun Liu from Hefei University of Technology China. “Upon further preparation and closer inspection, we discovered something unusual.”
The embryo was located inside the rib cage, facing forward. In comparison, swallowed animals usually face backward as a result of predators swallowing their prey head-first. This has also been confirmed when the team found that the baby was the same species of the mother.
“Further evolutionary analysis revealed the first case of live birth in such a wide group containing birds, crocodilians, dinosaurs and pterosaurs among others, and pushes back evidence of reproductive biology in the group by 50 million years,” Liu explains. “Information on reproductive biology of archosauromorphs before the Jurassic Period was not available until our discovery, despite a 260 million-year history of the group.”
According to Chris Organ , a professor at Montana State University, the fossil reveals that live birth is also related to sex determination of the offspring. The sex of some reptiles is determined by the temperature of the nest but Dinocephalosaurus determined the sex of its baby like birds and mammals.
Mike Benton, a professor at the University of Bristol, the findings could also indicate that archosauromorphs probably evolved live birth. The study also provides further understanding of a major dinosaur group.