via Live Science

About 90 million years ago, a giant tortoise used to live in what is today China. It laid a clutch of eggs that were the size of a tennis ball. An extremely thick eggshell, if not the thicker shell found in history.

Fortunately for the paleontologists, an egg never hatched and remained intact for tens of millions of years, preserving the delicate bones of the embryonic tortoise it contained. The egg fossil was then discovered in 2018.

Scientists are now running a series of analyses of this egg since its embryo is so rare that marks the first time that scientists have been able to identify the species of a dinosaur – old embryonic turtle.

In 2018, a farmer discovered in Henan province, China, a tennis-ball-sized egg and immediately donated it to a university. The egg was from the land turtle Yuchelys nanyangensis tortoise, which became extinct 66 million years ago at the end of the Cretaceous period, just when the dinosaur-killing asteroid hit land.

The clutches of eggs were likely buried in nests deep in moist soil to prevent them from drying out in the arid environment of central China during the late Cretaceouss, according to a study made by LiveScience.

This type of underground nesting and the thick eggshell served for these terrestrial turtles since they couldn’t adapt to colder climatic changes.

“The Y. nanyangensis egg, however, persisted because it is a one-egg tank”, says researcher Darla Zelenitsky, an associate professor of paleobiology at the University of Calgary in Canada.

The eggshell measures 2.1 by 2.3 inches (5.4 by 5.9 centimeters), making it a nearly spherical egg. The egg found is slightly smaller than a tennis ball. That’s larger than the eggs of most live tortoises and only slightly smaller than the eggs of Galapagos tortoises, Zelenitsky said.

The eggshell was put into a study to predict the size of the tortoiseshell and the results were remarkable. The study revealed that this thick egg was likely laid by a tortoise with a shell 5.3 feet long (1.6 meters). That measurement doesn’t include neck or head length, so mother turtle was easy as long as some humans were tall.