Devonian arthrodire embryos and the origin of internal fertilization in vertebrates

@article{Long2009DevonianAE,
  title={Devonian arthrodire embryos and the origin of internal fertilization in vertebrates},
  author={John A. Long and Kate Trinajstic and Zerina Johanson},
  journal={Nature},
  year={2009},
  volume={457},
  pages={1124-1127}
}
Evidence of reproductive biology is extremely rare in the fossil record. Recently the first known embryos were discovered within the Placodermi, an extinct class of armoured fish, indicating a viviparous mode of reproduction in a vertebrate group outside the crown-group Gnathostomata (Chondrichthyes and Osteichthyes). These embryos were found in ptyctodontids, a small group of placoderms phylogenetically basal to the largest group, the Arthrodira. Here we report the discovery of embryos in the… 

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