The oldest known amniotic embryos suggest viviparity in mesosaurs

@article{Pieiro2012TheOK,
  title={The oldest known amniotic embryos suggest viviparity in mesosaurs},
  author={Graciela Pi{\~n}eiro and Jorge Ferigolo and Melitta D. Meneghel and Michel Laurin},
  journal={Historical Biology},
  year={2012},
  volume={24},
  pages={620 - 630}
}
The earliest undisputed crown-group amniotes date back to the Late Carboniferous, but the fossil record of amniotic eggs and embryos is very sparse, with the oldest described examples being from the Triassic. Here, we report exceptional, well-preserved amniotic mesosaur embryos from the Early Permian of Uruguay and Brazil. These embryos provide the earliest direct evidence of reproductive biology in Paleozoic amniotes. The absence of a recognisable eggshell and the occurrence of a partially… 
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