By Greg Bear
June 16, 2014
Scientists do the heavy lifting--and I’m always happy when they confirm my suspicions. Especially about dinosaurs! A recent issue of SCIENCE highlights the work of John M. Grady, Brian J. Enquist, Eva Dettweiler Robinson, Natalie A. Wright, and Felisa A. Smith, who through analysis of fossil vertebrates conclude that the old dichotomy of cold-blooded vs. warm-blooded doesn’t really apply to dinosaurs--who instead likely practiced “mesothermy.” Lovely work!
"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." - Science, June 13, 2014
In DINOSAUR SUMMER we meet the lively dinosaurs of Venezuela’s Lost World, described as mesotherms. Here’s a sample of a young man’s introduction to the alternate paleontology of 1947--in a world where scientists could actually study live dinosaurs!
(1998 - ebook available from Open Road Media)
‘Don’t be fooled by their pretty eyes,’ Shellabarger said. ‘They don’t think like bears or big cats, or like any mammal.’ Shellabarger lifted the canvas cover. Inside the cage, a leggy creature as tall as a man lifted its smooth flexible neck and puffed out its throat below a toothless pointed jaw. Its long naked tail twitched like a cat’s, with a slow horizontal curl at the end. It seemed to be covered with brown and gray fur, but as it stalked forward, neck bobbing, and squeaked again, then whistled, Peter saw the fur was really a fine down of primitive feathers. Its eyes gleamed a beautiful golden color, mottled with rich chocolate specks, and the inside of its mouth and tongue was lavender.
Instead of wings it had long agile three-clawed hands. The claws gripped the bars and it angled its head to peer at Shellabarger.
‘This is Dip,’ the trainer said. ‘He’s not a bird or an avisaur–he’s a real dinosaur. A plains struthio. Scientists call him a ratite mesotherm.’ He twisted his mouth in distaste. ‘I like the Indian names better. Does it look like a sadashe tonoro, or like a Neostruthiomimus planensis?’