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Re: The origin of turtles: A paleontological perspective

Note that the pdf of this paper is now free:


On Wed, Feb 25, 2015 at 10:35 AM, Ben Creisler <bcreisler@gmail.com> wrote:
> Ben Creisler
> bcreisler@gmail.com
> A new online paper:
> Walter G. Joyce (2105)
> The origin of turtles: A paleontological perspective.
> Journal of Experimental Zoology Part B: Molecular and Developmental
> Evolution (advance online publication)
> DOI: 10.1002/jez.b.22609
> http://onlinelibrary.wiley.com/doi/10.1002/jez.b.22609/abstract
> The origin of turtles and their unusual body plan has fascinated
> scientists for the last two centuries. Over the course of the last
> decades, a broad sample of molecular analyses have favored a sister
> group relationship of turtles with archosaurs, but recent studies
> reveal that this signal may be the result of systematic biases
> affecting molecular approaches, in particular sampling, non-randomly
> distributed rate heterogeneity among taxa, and the use, and the use of
> concatenated data sets. Morphological studies, by contrast, disfavor
> archosaurian relationships for turtles, but the proposed alternative
> topologies are poorly supported as well. The recently revived
> paleontological hypothesis that the Middle Permian Eunotosaurus
> africanus is an intermediate stem turtle is now robustly supported by
> numerous characters that were previously thought to be unique to
> turtles and that are now shown to have originated over the course of
> tens of millions of years unrelated to the origin of the turtle shell.
> Although E. africanus does not solve the placement of turtles within
> Amniota, it successfully extends the stem lineage of turtles to the
> Permian and helps resolve some questions associated with the origin of
> turtles, in particular the non-composite origin of the shell, the slow
> origin of the shell, and the terrestrial setting for the origin of
> turtles.