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The origin of turtles: A paleontological perspective

Ben Creisler

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

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