Turtles all the way down: loggerheads at the root of the chelonian tree

@article{Lyson2009TurtlesAT,
  title={Turtles all the way down: loggerheads at the root of the chelonian tree},
  author={Tyler R. Lyson and Scott F. Gilbert},
  journal={Evolution \& Development},
  year={2009},
  volume={11}
}
The recent discovery of the oldest and most primitive stem turtle, Odontochelys semitestacea (Li et al. 2009), from the lower Upper Triassic of China reopens the debate regarding the origin of the turtle shell, the paleoecology of basal turtles (terrestrial or aquatic), and the placement of turtles among amniotes. The debate surrounding the origin of the shell dates back to Cuvier (1800–1805) with two competing hypotheses. The de novo hypothesis, argues that the carapace (dorsal shell) formed… 
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