Re: _Odontochelys semitestacea_ comes out of its shell

[David Marjanovic <david.marjanovic@gmx.at>]

> See: http://www.nature.com/news/2008/081126/full/news.2008.1260.html

Strangely, I have full access and can therefore post a few more quotes:

> >
One of the study's authors, Chun Li, from the Institute of Vertebrate 
Paleontology and Paleoanthropology at the Chinese Academy of Sciences, told 
Nature News, "[The fossil] could be seen as the missing link of turtle 
evolution. We found how the turtle shell formed. It is not derived from a 
fusion of osteoderms."
"It is the first fossil evidence to show that the turtle may have originated 
from a water rather than land environment," he says.
But Robert Reisz and Jason Head, palaeontologists at the University of 
Toronto in Mississauga, Canada, disagree with the team's interpretation of 
the shell's origin [reference 2]. Reisz and Head propose that the absence of 
the carapace is an adaptation to living in a marine environment.
"This is a very exciting discovery," says Reisz, speaking on the Nature 
podcast [link].
<<

> >
Walter Joyce, a palaeontologist, who will take up a position at the 
University of TÃbingen, Germany, in the new year, is equally excited by the 
new find but agrees that questions remain over the origins of the shell.
"The specimen does not answer the question of whether this is the basal 
condition or not," he says. "This is unbelievable material. This specimen is 
a blessing and a curse because it throws everything back up in the air 
again."
But another of the study's authors, Olivier Rieppel, of the department of 
geology at the Field Museum in Chicago, Illinois, says the view that the 
shell is reducing is wrong. He says the shell formation seen in the fossil 
more closely resembles that of embryonic turtle shells than that of extant 
aquatic turtles. This supports his team's interpretation that the two parts 
of the shell evolved separately, says Rieppel.
"If you look at aquatic turtles alive today that have reduced carapace, none 
match the patterns seen in the fossil. Our fossil looks like the embryonic 
pattern," he says.
<<

References:
> >
Li, C., Wu, X.-C., Rieppel, O., Wang, L.-T. & Zhao, L.-J. Nature 456, 
497â501 (2008).
Reisz, R. R. & Head, J. J. Nature 456, 450â451 (2008).
<<

Well, I'm glad that this was published early enough to be used in my PhD 
thesis on amniote phylogeny and the origin of turtles. I like living in 
interesting times. :-)