News | Evolution

Evidence is mounting against claims that dinosaurs could not have been endothermic, including a new analysis of fossil microstructures found in ruminants, lizards, dinosaurs and crocodiles

By Brian Switek and Nature magazine | June 27, 2012|

Studying modern mammals can provide insights into the metabolism of dinosaurs. Image: Walter Myers /Stocktrek Images/Corbis

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From Nature magazine

From museums to Hollywood films, dinosaurs are portrayed as highly active animals, but how they maintained this lifestyle isnt clear. For decades, palaeontologists have debated whether the physiology of non-avian dinosaurs was akin to that of today's cold-blooded reptiles or warm-blooded mammals. An important clue has now been uncovered not in Triceratops and its relatives, but in herbivorous mammals.

Palaeontologists have often examined bone microstructure in their investigations of dinosaur growth and physiology. Key to arguments on the subject are lines of arrested growth (LAGs) that represent an annual slowdown typically tied to a cold or dry season during which resources are scarce. These rings are seen in dinosaurs, as well as in creatures such as lizards and crocodiles, whose body temperatures are regulated by the external environment, but have not often been observed in the bones of endotherms creatures such as mammals that maintain high, constant body temperatures. But in a study published today in Nature, palaeontologist Meike Khler at the Autonomous University of Barcelona in Bellaterra, Spain, and her colleagues report that LAGs are present in ruminants from the tropics to the poles, greatly altering the context of the dinosaur-physiology debate.

Read more:
Dinosaurs Might Have Had Warm-Blooded Animals' Fast Metabolism