Warm-blooded advantage

Giant reptiles that lived in the seas hundreds of millions of years ago had a constant body temperature

Geochemists and paleontologists from the Lyon laboratory “Palaeoenvironment and Paleobiosphere” managed to answer a question that has long haunted scientists: how did the contemporaries of dinosaurs - the giant reptiles that inhabited the oceans in those ancient times - regulate heat exchange? Were they, like today's mammals and birds, warm-blooded animals, or were they cold-blooded, like fish and modern reptiles?

According to an article published in the journal Science, the huge reptiles that ruled the oceans like dinosaurs did on land were warm-blooded. Constant body temperature gave them a significant advantage - it allowed them to swim far and quickly.

French scientists have calculated the body temperature of three main groups of reptiles that lived with dinosaurs during the Mesozoic era (200 - 65 million years ago): ichthyosaurs, plesiosaurs and mosasaurs. The content of stable oxygen isotopes 160 and 180 in the phosphates of the skeletons of these animals was used as a thermometer. The researchers analyzed the teeth of ichthyosaurs, plesiosaurs and mosasaurs and compared the ratio of 160 and 180 in the tooth enamel of these reptiles and in the remains of fish that lived at the same time.

Fish, which then, as now, were cold-blooded, have an isotopic composition that reflects the temperature of the sea water in which they lived. In fish, the ratio between 160 and 180 increases with decreasing water temperature. Based on differences in the isotopic composition of marine reptiles and fish that lived in the same bodies of water, scientists drew conclusions about the difference in their body temperatures.

Geochemists and paleontologists from Lyon came to the conclusion that the body temperature of giant reptiles was constant regardless of water temperature, i.e. they can be classified as warm-blooded animals. They regulated their body temperature independently of the seawater temperature within a temperature range of 35 to 39°C (plus or minus 2°C).

This heat exchange allowed the long-extinct ichthyosaurs, plesiosaurs, mosasaurs and a number of other reptiles to maintain a higher temperature than the ambient temperature. As a result, they could move faster and swim long distances even in cold water, dive deeper, i.e. gained an advantage over competitors. It is not surprising that these animals lived for one and a half hundred million years.

Zakhar RADOV