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Giant plant-eating lizard from Eocene of Asia competed with mammals (free pdf)



From: Ben Creisler
bcreisler@gmail.com

A new non-Mesozoic paper that may be of interest. It's open access.

Jason J. Head, Gregg F. Gunnell, Patricia A. Holroyd, J. Howard
Hutchison and Russell L. Ciochon (2013)
Giant lizards occupied herbivorous mammalian ecospace during the
Paleogene greenhouse in Southeast Asia.
Proceedings of the Royal Society B  280 (1763) 20130665
doi: 10.1098/rspb.2013.0665
http://rspb.royalsocietypublishing.org/content/280/1763/20130665.abstract

Mammals dominate modern terrestrial herbivore ecosystems, whereas
extant herbivorous reptiles are limited in diversity and body size.
The evolution of reptile herbivory and its relationship to mammalian
diversification is poorly understood with respect to climate and the
roles of predation pressure and competition for food resources. Here,
we describe a giant fossil acrodontan lizard recovered with a diverse
mammal assemblage from the late middle Eocene Pondaung Formation of
Myanmar, which provides a historical test of factors controlling body
size in herbivorous squamates. We infer a predominately herbivorous
feeding ecology for the new acrodontan based on dental anatomy,
phylogenetic relationships and body size. Ranking body masses for
Pondaung Formation vertebrates indicates that the lizard occupied a
size niche among the larger herbivores and was larger than most
carnivorous mammals. Paleotemperature estimates of Pondaung Formation
environments based on the body size of the new lizard are
approximately 2–5°C higher than modern. These results indicate that
competitive exclusion and predation by mammals did not restrict body
size evolution in these herbivorous squamates, and elevated
temperatures relative to modern climates during the Paleogene
greenhouse may have resulted in the evolution of gigantism through
elevated poikilothermic metabolic rates and in response to increases
in floral productivity.

News release:

http://newsroom.unl.edu/releases/2013/06/04/%27Lizard+King%27+fossil+shows+giant+reptiles+coexisted+with+mammals+during+globally+warm+past