(ORDO NEWS) — Modern whales often give birth in warm coastal waters, where there is little food, but not many predators.
Now scientists have found that 200 million years ago, giant marine reptiles, late Triassic ichthyosaurs the size of a bus, behaved the same way.
In the late Triassic, about 200 million years ago, marine reptiles swam in the seas of our planet – ichthyosaurs.
Although most of the species of these animals that inhabited the seas of the Jurassic and Cretaceous periods were the size of a dolphin, real giants lived in the Triassic period, reaching at least 15 meters in length.
One such species was Shonisaurus popularis , and the Humboldt-Toiyabe National Forest in Nevada ( USA) hosts one of the largest burials of these reptiles – there are several dozen of them.
For many years, paleontologists have puzzled over why these animals died there, putting forward a variety of assumptions – from mass beaching, like today’s whales, to poisoning with “blooming” water.
To put an end to this issue, an international team of researchers from the US, UK and Belgium decided to thoroughly study the excavation site, paying attention not only to the bones themselves, but also to the rock surrounding them.
After collecting samples of the stone surrounding the skeletons in the national forest (most of the bones are still in the ground, and tourists can look at them in their natural position), scientists clarified the circumstances of the burial and checked whether the animals were killed by a volcanic eruption, a “bloom” of water, or what something else.
It turned out that shonisaurs died under normal conditions, and the carcasses sank to the seabed, and were not washed ashore.
Curiously, besides ichthyosaurs, there are few large animals in the fossil stratum – neither fish nor other reptiles – so the picture comes out intriguing: a certain area of the sea is literally crammed with giant lizards who have come together for a purpose.
Finally, the last piece of the puzzle was found in the museum’s collection: tiny bones that belonged to a baby ichthyosaur that had just been born.
With a high degree of probability, the adult shonisaurs that gathered in these unfeeding waters were pregnant females, just about ready to give birth to offspring.
After analyzing the age of the various layers in which the bones lie, the scientists found that the shonisaurs did not die here at the same time, there is a time difference between the youngest and oldest fossils of thousands, if not millions of years.
In other words, what we have before us is not evidence of the mass death of animals, but a long-term cemetery, to which only a small part of too old or weak females who did not survive the process of underwater childbirth went.
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