Oldest Amniote Embryos Hint Early Reptiles Gave Birth Alive
Brazilian and Uruguayan fossils from the Early Permian reveal 280-million-year-old mesosaur embryos preserved inside adults and an isolated egg, suggesting mesosaurs may have retained embryos in the uterus or laid eggs at late development; this finding pushes the oldest known amniote embryos and earliest viviparity back by about 60 million years, offering rare insights into reproduction and potential parental care in Paleozoic reptiles.
