Live birth in an archosauromorph reptile
Scientists report the discovery of a pregnant long-necked marine reptile (Dinocephalosaurus) from the Middle Triassic (∼245 million years ago) of southwest China showing live birth in archosauromorphs. Dinocephalosaurus was a member of the archosaur family, which includes extinct dinosaurs as well as today’s birds and crocodiles — all egg-layers.
The discovery pushes back evidence of reproductive biology in the clade by roughly 50 million years, and shows that there is no fundamental reason that archosauromorphs could not achieve live birth. The phylogenetic models indicate that Dinocephalosaurus determined the sex of their offspring by sex chromosomes rather than by environmental temperature like crocodilians.
This discovery may rewrites our understanding of the evolution of reproductive systems.
