Prehistoric Marvel: Farmer’s Discovery of Fossilized Giant Turtle Egg Unveils Perfectly Preserved Baby Within

The turtle that laid the egg may have had a shell as long as a person is tall, roaming the Earth alongside the dinosaurs.

Han and Jiang, who are based at the China University of Geosciences in Wuhan, initially thought the egg might have come from a new dinosaur species. But careful analysis revealed something even rarer. Entombed in the egg’s rocky confines lay the remains of a giant extinct turtle.

The fossilized egg from the Cretaceous period, containing a rare turtle embryo inside.

“These were not small turtles by any stretch,” says Darla Zelenitsky, an author of the new study and a paleontologist at the University of Calgary in Alberta, Canada.

Reconstructing the tiny turtle

The embryo is strikingly similar to modern turtles, says Raul Diaz, a reptile evolutionary biologist specializing in embryos at California State University, Los Angeles. He points to the embryo’s flat ribs, which would have hardened and spread as the turtle grew to form the underlying structure of its protective shell. “It’s almost—in my head—indistinguishable from what I would see in the lab,” says Diaz, who was not part of the new study.

However, there were a few key features that helped identify the ancient turtle’s specific group. The upper jawbone, for example, bears a strong resemblance to nanhsiungchelyids, Zelenitsky says, due to its slightly square shape and serrated back edge.

Tough eggshells

The exact purpose of the ancient turtle’s tough eggshells is uncertain. The thickness may be an adaptation to the arid climate that is believed to have existed at the time, inferred from plant life found in the same rock formation as the egg. A thick shell would have limited the amount of water that escaped from the egg. Alternatively, the shell could have prevented the eggs from breaking if the turtles dug deep nests underground.

Regardless of the thick shell’s purpose, Zelenitsky says, “I don’t know how they got out.” The newborn turtles must have had to rigorously flex and extend their limbs in their attempts to hatch.

Wiped out with the dinosaurs

The fact that nanhsiungchelyid turtles lived and nested on land may have contributed to their demise. The group died out alongside all non-avian dinosaurs some 66 million years ago, when a colossal asteroid hurtled into Earth. The impact sent out a blast of energy that flung sizzling hot rock into the skies and ignited vast tracts of land. “Anything that was on the surface got boiled,” Lyson says.

Turtle eggshells like the nanhsiungchelyids’ were not seen again after the impact, and the researchers suggest that perhaps the thick shells were unsuited to the dramatic shift in the environment. But more information is necessary to figure out exactly why the thick shells disappeared.