Tyrannosaurus and brontosaurs were warm to the touch

On the one hand, dinosaurs are reptiles, and reptiles, as we know, are cold-blooded animals: their own metabolism heats them weakly, their body temperature depends on the environment. On the other hand, modern birds, the most warm-blooded of the warm-blooded, descended directly from dinosaurs (in fact, the birds themselves are now called that – surviving dinosaurs). What were the tyrannosaurs themselves, triceratops, stegosaurs and many, many others – cold-blooded or warm-blooded?

We cannot measure the temperature of a living dinosaur, but we can estimate the level of metabolism. There are different methods here. For example, fast or slow metabolism is indicated by fast or slow bone growth, and we wrote about one study that concluded that dinosaurs were neither truly warm-blooded nor truly cold-blooded, and should be called semi-warm-blooded. But here the difficulty arises in how to relate the growth rate that we see in the bones to the metabolic rate. Animals can grow at different rates in different periods of life, and if we have only their remains on our hands, then we risk making a big mistake about them.

Another option is to analyze the proportions of different isotopes in the same remains: depending on the metabolism, the proportions of isotopes will change. So did the authors of another study, which we also wrote about; but even in this case, the dinosaurs turned out to be “warm-blooded, as it were.” The isotopic method of measuring temperature also has its weaknesses: for example, it is possible that the number of isotopes in the remains changes when they are fossilized.

Employees Yale University proposed another method: to determine the level of metabolism, you need to estimate the oxygen consumption. The more intense the metabolism, the more oxygen the body absorbs, but also the more molecular oxidized debris appears in it. Oxygen and its compounds inevitably react with proteins, lipids, carbohydrates, making them unsuitable for cellular work – some of them are destroyed and disappear from the body, but some still remain. What is important, this debris is quite stable and is quite preserved in the fossilized remains. Such molecular markers can provide more reliable information about metabolism than isotopes and minerals in bones.

In an article in Nature the researchers describe how they used Raman and infrared Fourier spectroscopy to study the accumulated oxidized organic debris in the bones. For analysis, samples were taken from several dozen femurs belonging to both various fossil pangolins and modern birds, animals and reptiles. Dinosaurs are divided into two large groups, lizard and ornithischian, depending on the structural features of the pubic bones. Ornithischians include, for example, triceratops and stegosaurs, and their metabolism, apparently, was like that of modern cold-blooded ones.

But the lizards were warm-blooded, and even very warm-blooded – some of them had a metabolic rate similar to that of birds, and the body temperature of birds, as you know, is on average higher than that of animals. Perhaps this is not surprising: the immediate ancestors of birds belong to the lizards (yes, birds did not originate from ornithischians, but from lizards). In addition, warm-blooded lizards include predatory “tyrannosaurus-like” lizards that ran on two legs, and huge herbivorous sauropods – diplodocus, brontosaurs, brachiosaurs, etc. If we had to touch a tyrannosaurus rex or brontosaurus, we would find that they are warm to the touch . Just as warm were the pterosaurs, which are considered a separate group of reptiles, quite far removed from the dinosaurs. And, most likely, in aquatic plesiosaurs, the metabolism was also active enough to be considered partly warm-blooded.

It turns out that birds were far from the first dinosaurs to become truly warm-blooded. Herbivorous giant sauropods did not fly, did not flap their wings, and generally did not lead a very energetic lifestyle, however, their metabolic rate was quite high. Warm-bloodedness appeared in them due to some other evolutionary reasons. In the same way, it cannot be said that the bird line of dinosaurs survived during the extinction due to warm-bloodedness – many pangolins with a bird-like metabolic rate then died out safely.

New data also helps to understand some of the ecological features of different groups of dinosaurs. For example, it is obvious that cold-blooded lizards had to look for warmer places to live, and, most likely, they even migrated during the seasonal cold. And brontosaurs and diplodocus had to have an exceptionally efficient digestive system, otherwise, with their warm-bloodedness, they would not have grown to such sizes.

Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.

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