Earth’s oldest amphibians grew very fast in their first years of life

(ORDO NEWS) — American scientists have found that watchers, one of the first amphibians of the Earth, grew very quickly in the first stages of life, which contradicts the established ideas about the slow metabolism of the most ancient amphibians.

“When I discovered traces of the rapid growth of these reptiles during their childhood and adolescence, I immediately contacted my colleagues.

I informed them that our discovery casts doubt on all generally accepted ideas about how the growth process of ancient amphibians changed as they evolution,” said Megan Whitney, a professor at Loyola University in Chicago (USA), quoted by the press service of the Field Museum.

The exact time and history of the appearance of amphibians is still a mystery to paleontologists. This is due to the fact that at the time of the appearance of transitional forms between amphibians and fish, about 370-350 million years ago, the so-called Romer’s failure occurs.

It lies in the fact that the remains of the first amphibians and “fish-animals” for reasons not yet clear to us are extremely rare in the rocks of the Devonian and Carboniferous period.

For this reason, we know only a few bizarre animals of this era, including the primitive amphibians pederpes, watcheria and acanthostega, as well as the Tiktaalik fish.

Their remains have been discovered mainly in the last ten years thanks to excavations in northern Canada and the United States. So far, scientists cannot say exactly where these primitive tetrapods lived, what they ate and what role they could play in ancient ecosystems.

The life of the oldest amphibians of the Earth

Whitney and her colleagues took a big step toward unraveling the life history of these ancient amphibians by studying nine recently discovered remains of the Watcheria, a large amphibian that lived in tropical seas in what is now the northern United States approximately 350-340 million years ago.

These amphibians reached a length of about two meters and were supposedly the largest vertebrate predators of their era.

Paleontologists noticed that the femurs of the watchers they studied were so well preserved that inside them there are peculiar “growth rings” that appear inside the bone tissue during its growth.

Based on this pattern, the scientists analyzed and compared the structure and size of these “annual rings” in the bones of young and adult watchers, which allowed them to study the growth process of these amphibians.

Initially, scientists expected that the “growth rings” in the bones of the watchers would be approximately the same size, which would reflect the slow and even process of their growth, presumably characteristic of ancient and modern amphibians and reptiles.

Unexpectedly, it turned out that the watchers were more similar in this respect to modern birds and mammals – they grew rapidly in the first years of life, but then the process of their growth was sharply inhibited.

As scientists suggest, rapid growth in the first years of life helped watchers reach those sizes at which they became invulnerable to other predators, and could also easily hunt other inhabitants of land and seas.

Professor Whitney and her colleagues hope that subsequent searches and studies of other amphibians from the Romer Gap will help scientists understand what caused amphibians to abandon this survival strategy in subsequent geological epochs.

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