Transitional fossils and the origin of turtles

@article{Lyson2010TransitionalFA,
  title={Transitional fossils and the origin of turtles},
  author={Tyler R. Lyson and Gabriel S Bever and Bhart‐Anjan S. Bhullar and Walter G. Joyce and Jacques A. Gauthier},
  journal={Biology Letters},
  year={2010},
  volume={6},
  pages={830 - 833}
}
The origin of turtles is one of the most contentious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile–bird clade, (ii) the lizard–tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard–tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the ‘parareptile’ Eunotosaurus africanus results in a single overriding… 

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TLDR
A new reptile, Pappochelys, is reported that is structurally and chronologically intermediate between Eunotosaurus and Odontochelys and dates from the Middle Triassic period (∼240 million years ago), providing new evidence that the plastron partly formed through serial fusion of gastralia.
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