Friday, 31 May 2013

Now It's Transitional Turtle Fossils

BBC News - How the turtle got its unique hard shell

What an appalling day for Creationists!

What with pebbles on Mars showing how Mars is very old and the 'Goldilocks zone' is much wider that they like to pretend, transitional fossils showing how cretaceous amphibians evolved, the discovery of rapid recent evolution in Brazilian palm trees and news that scientists at CERN are getting closer to explaining why matter exists, the news of the discovery of a transitional turtle fossil must be devastating.

If they don't adopt their normal method of coping with the cognitive dissonance and simply covering their eyes until it goes away, that is.

Summary
The origin of the turtle shell has perplexed biologists for more than two centuries. It was not until Odontochelys semitestacea was discovered, however, that the fossil and developmental data could be synthesized into a model of shell assembly that makes predictions for the as-yet unestablished history of the turtle stem group. We build on this model by integrating novel data for Eunotosaurus africanus—a Late Guadalupian (∼260 mya) Permian reptile inferred to be an early stem turtle. Eunotosaurus expresses a number of relevant characters, including a reduced number of elongate trunk vertebrae (nine), nine pairs of T-shaped ribs, inferred loss of intercostal muscles, reorganization of respiratory muscles to the ventral side of the ribs, (sub)dermal outgrowth of bone from the developing perichondral collar of the ribs, and paired gastralia that lack both lateral and median elements. These features conform to the predicted sequence of character acquisition and provide further support that E. africanus, O. semitestacea, and Proganochelys quenstedti represent successive divergences from the turtle stem lineage. The initial transformations of the model thus occurred by the Middle Permian, which is congruent with molecular-based divergence estimates for the lineage, and remain viable whether turtles originated inside or outside crown Diapsida.


Lead author, Dr Lyson, of the Smithsonian Institute and Yale University, described the fossil thus:

Eunotosaurus is a good transitional fossil which bridges the morphological gap between turtles and other reptiles. [My emphasis]

I hope any Creationists who have lasted this far noted that description. If so, they won't now in all honesty be able to use the traditional Creationist argument that there are no transitional fossils.
The turtle shell is considered an evolutionary novelty, which means that there are no closely analogous structures in related animals.

That leads to the notion that such things cannot occur through normal evolutionary processes. But, when you examine it in detail, you can see the series of steps, each of them explainable through small changes that gradually add up to the novel structure.
Judith Cebra-Thomas, assistant professor from the department of biology at Millersville University in Pennsylvania.
(Quoted by Melissa Hogenboom, Science Reporter BBC News)
There we have as good a description of Darwinian evolution as you'll find anywhere - "[a] series of steps, each of them explainable through small changes that gradually add up to the novel structure". And the whole is, of course, what Creationist 'scientists' like Michael Behe and the professional liars of the Discovery Institute would describe as 'irreducibly complex' and therefore evidence of their current under-cover version of biblical literalism, 'Intelligent Design'.

It has been a very bad day indeed for these frauds.

Reference:
Evolutionary Origin of the Turtle Shell; Tyler R. Lyson, Gabe S. Bever, Torsten M. Scheyer, Allison Y. Hsiang, Jacques A. Gauthier; Current Biology - 30 May 2013

How the turtle got its unique hard shell; Melissa Hogenboom, Science reporter, BBC News, 31-May-2013

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