Scientists have found an egg of a prehistoric turtle with an embryo preserved inside

Scientists have found an egg of a prehistoric turtle with an embryo preserved inside
Scientists have found an egg of a prehistoric turtle with an embryo preserved inside

An international team of scientists from Canada and China presented the results of a study of a fossilized turtle egg from the Cretaceous period. Such an object is already very rare in itself, since the fragile shell does not stand the test of time. But what is especially unique is that a fossilized embryo remains inside the well-preserved egg.

The find in 2018 was made by a farmer from the Chinese province of Henan. Digging the ground, he came across stones that looked rather unusual, and decided to show them to scientists. Paleontologists immediately recognized the "stones" as eggs, but these fossils, which resemble billiard balls in size and shape, were unlike any dinosaur egg they had seen before.

In the course of research, it was found that these are turtle eggs laid 66-145 million years ago. The animal belonged to the extinct group of Nanhsiungchelyids turtles. It is known that these reptiles were gigantic in size. Several of their fossils are already at the disposal of scientists. The length of the shell of the Nanhsiungchelyids averaged 1.5 meters.

Paleontologists have almost no opportunity to examine the embryos of prehistoric turtles: even if the shells remain for centuries, the delicate tissues of the embryo cannot cope with this challenge. The farmer's find is the only specimen that can be called almost perfect. Even the rest of the eggs, laid at the same time, collapsed over time.

Scientists scanned the egg using microcomputer tomography, which allows you to look under the shell without having to break its integrity. Inside was a "tangle of scattered bones." The team reconstructed each bone in three dimensions and then modeled a tiny turtle skeleton.

In general, the embryo is "strikingly similar" to modern turtles. The flat ribs of the embryo likewise hardened and expanded as it grew to form the basic structure of the carapace in the future. However, there were also several key features that helped identify the species. In particular, all Nanhsiungchelyids have a characteristic square-shaped maxilla with a serrated trailing edge.

The most unusual feature was the strength of the shell. For all known turtles, the thickness, although different depending on the species, is usually not stronger than paper. Here, the 2 mm thick shell turned out to be four times more massive than that of the eggs of the largest modern giant, the Galapagos tortoise.

There is no explanation for this: from the point of view of the laws of nature, this can even be called an unnecessary precaution: the reptile spends additional resources on forming a too dense shell, and it is more difficult for the baby to get out of it. Paleontologists speculate that the increased hardness may have been a response to an arid climate and limited the flow of fluid from the egg.

The fact that the Nanhsiungchelyids lived and nested on land could be the reason for their death: this group became extinct at the same time with all non-avian dinosaurs about 66 million years ago, when a colossal asteroid crashed into Earth. At the same time, the river relatives of the Nanhsiungchelyids survived the disaster by hiding under water. In addition, diet could play a role in the extinction of the group: these turtles ate exclusively on plants, and after the fall of the asteroid, their number became much less.

The study of the unique find continues, and scientists hope to learn more about the evolution of turtles.

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