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Dinosaurs as "mesotherms"



Ben Creisler
bcreisler@gmail.com

A new paper:

John M. Grady, Brian J. Enquist, Eva Dettweiler-Robinson, Natalie A.
Wright & Felisa A. Smith (2014)
Evidence for mesothermy in dinosaurs.
Science 344 no. 6189: 1268-1272
DOI: 10.1126/science.1253143
http://www.sciencemag.org/content/344/6189/1268

Were dinosaurs ectotherms or fast-metabolizing endotherms whose
activities were unconstrained by temperature? To date, some of the
strongest evidence for endothermy comes from the rapid growth rates
derived from the analysis of fossil bones. However, these studies are
constrained by a lack of comparative data and an appropriate energetic
framework. Here we compile data on ontogenetic growth for extant and
fossil vertebrates, including all major dinosaur clades. Using a
metabolic scaling approach, we find that growth and metabolic rates
follow theoretical predictions across clades, although some groups
deviate. Moreover, when the effects of size and temperature are
considered, dinosaur metabolic rates were intermediate to those of
endotherms and ectotherms and closest to those of extant mesotherms.
Our results suggest that the modern dichotomy of endothermic versus
ectothermic is overly simplistic.
**
Commentary:

Michael Balter (2014)
Dinosaur metabolism neither hot nor cold, but just right.
Science  344 no. 6189: 1216-1217
DOI: 10.1126/science.344.6189.1216
http://www.sciencemag.org/content/344/6189/1216.summary

Paleontologists have struggled for 50 years to determine whether
dinosaurs were cold-blooded like today's reptiles or warm-blooded like
most modern mammals and birds. A study on page 1268 examines the
growth and metabolic rates of nearly 400 living and extinct animals,
and concludes that neither was right. Instead, dinosaurs had an
in-between metabolism.
**

Blogs:

http://phenomena.nationalgeographic.com/2014/06/12/dinosaurs-tuna-great-whites-echidnas/