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Latest Cretaceous Polar Dinosaurs

Naturwissenschaften. 2008 Dec 16.
The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs 
in Russia.Godefroit P, Golovneva L, Shchepetov S, Garcia G, Alekseev P.
Department of Palaeontology, Royal Belgian Institute of Natural Sciences, rue 
Vautier 29, 1 000, Brussels, Belgium, Pascal.Godefroit@naturalsciences.be.
A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil 
assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs 
were still highly diversified in Arctic regions just before the 
Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, 
belonging to hadrosaurids and non-avian theropods, indicate that at least 
several latest Cretaceous dinosaur taxa could reproduce in polar region and 
were probably year-round residents of high latitudes. Palaeobotanical data 
suggest that these polar dinosaurs lived in a temperate climate (mean annual 
temperature about 10 degrees C), but the climate was apparently too cold for 
amphibians and ectothermic reptiles. The high diversity of Late Maastrichtian 
dinosaurs in high latitudes, where ectotherms are absent, strongly questions 
hypotheses according to which dinosaur extinction was a result of temperature 
decline, caused or not by the Chicxulub impact.