Eleventh.

Throughout these blogs I have tried to incorporate paleoclimatology with anatomy and physiology, in an attempt to see how the effects of climate fluctuations causes species to adapt (or in some cases, go extinct) to these new conditions. The most interesting fossil finds of the last decade and a half are the fossil feathered dinosaurs, especially from China, and I have touched on this subject a few weeks ago with my article on Yutyrannus. For this post we will be returning to China, with an article that enhances my aforementioned post on the largest feathered theropod and its implications on Cretaceous climate.

The Jehol Biota, named after a province in China, is arguably one of the finest fossil deposits on the planet, with immaculately preserved feathered dinosaurs, plants and invertebrates all being found, shedding light on the Early Cretaceous ecosystem. Thanks to such pristine preservation, a large team from France, China, Thailand and Japan examined the isotope concentrations in fossil structures such as teeth and bone. Air temperature alters the amount of certain oxygen isotopes contained in rainwater, which is drunk by animals. This "record" is then passed on during growth during bone and tooth formation, which is then preserved in the fossil record. They assigned the differences in isotope concentrations between dinosaur taxa to differences in water strategies, diet and microhabitat, as such differences are expected.  

What they found is mirrored in the Yutyrannus post a few weeks back. The idea of a entirely warm Cretaceous era was banished in favour of a new idea that during some stages, the climate was much like modern day climates at the same latitudes: a cool, temperate climate with harsh winters. This would have forced the ectothermic turtles and crocodiles, for example, to hibernate. Amoit (2011), lead author of the paper, wanted to make the appearance of feathers on dinosaurs clear: "These results do not prove in any way that feathers appeared because of their insulating characteristics. They show that feathers would have given the dinosaurs of the Jehol fauna a physiological advantage over their fellow animals with scales". 

Jehol Dinosaurians, characterised by feathers 

Its is therefore necessary, therefore, to continue research in these Chinese provinces, and perhaps look for feathered dinosaurs in Cretaceous rocks before this "cool" period set in, and examine the oxygen isotopes. If feathers are present in a large number of species, as they are in the Jehol rocks, even in warmer climes, we could predict that feathers were indeed used for reasons other than insulation. However, should the appearance of feathered species coincide with the decreasing temperatures, then it is understandable to reject Amoit's claim.

R. Amiot, X. Wang, Z. Zhou, X. Wang, E. Buffetaut, C. Lecuyer, Z. Ding, F. Fluteau, T. Hibino, N. Kusuhashi, J. Mo, V. Suteethorn, Y. Wang, X. Xu, F. Zhang. Oxygen isotopes of East Asian dinosaurs reveal exceptionally cold Early Cretaceous climates. Proceedings of the National Academy of Sciences, 2011
http://www.sciencedaily.com/releases/2011/03/110311173104.htm
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