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The bigger the dinosaur, the hotter it was

Scientists have researched, that Dinosaurs body temperatures depended on their sizes and the larger their size, the hotter their body temperature was.

india Updated: Jul 15, 2006 17:37 IST

Scientists have said, that dinosaurs body temperatures depended on their sizes and the larger their size, the hotter their body temperature was.

Some scientists have said that recent studies had revealed that reptiles could actively regulate their body temperatures just like mammals, while some others have said that they lost the heat generated by their metabolism so slowly, that they remained warm for a long time.

Now, Prof James Gillooly and colleagues from the University of Florida at Gainesville, US opine that both theories could be possibilities.

Prof. Gillooly and his team found that crucial biochemical reactions, common to all life forms depended on temperature. In other words, the relationship between temperature, metabolic or growth rate and body mass were all components of a simple equation that had few constants.

The equation worked across a wide variety of creatures, from planktons to blue whales, he said.

For their study, his team decided to apply their equation to eight species of dinosaurs, ranging in size from 12 kilograms to 13 tonnes. Data on growth rates, measured by other researchers from the annual rings seen in dinosaur bones and body mass estimates at different ages was compiled.

According to their equation, the body mass during maximum growth, combined with the growth rate, can be used to calculate temperature.

Findings revealed that bigger the dinosaur, the hotter it was. The smaller species were very much like modern reptiles, with body temperatures around 25 degrees centigrade, the ambient environmental temperature for their era. But as dinosaurs got bigger, and the ratio of their surface area to their volume fell, they became less efficient at dissipating metabolic heat – especially as they surpassed 600 kg.

The 13-tonne Apatosaurus, also known as Brontosaurus had a body temperature of 41 degrees Celsius, compared to the human body temperature of 37 degrees.

Studies on 11 species of the modern crocodile family taking into account the relationship between size and temperature also revealed the same temperature curve.

When the data was extrapolated to the biggest dinosaur, Sauroposeidon, a body temperature of 48 degrees Celsius was found – the limit at which normal tissue begins to break down.

This suggested that body temperature depended on the dinosaurs’ size, he said.

"The juvenile Apatosaurus had body temperatures 20 degrees Celsius less than their parents. So while young dinosaurs sunbathed like modern lizards, perhaps the larger dinosaurs needed to seek out water or shade to cool off, " Prof. Gillooly said.

The findings appear in the journal PloS Biology, reports New Scientist.