Fossilized eggs found from dinosaur with the longest claws in the history of life on Earth

Imagine a 25-foot tall dinosaur that fiercely protected its eggs with eight-foot arms wielding meter-long Freddy Krueger-like blades for fingernails and you’ve got the general idea of the Therizinosaurus. These fearsome creatures may have weighed up to five tons and once prowled around the location of today’s Gobi Desert in Mongolia.

Hokkaido University’s Yoshitsugu Kobayashi found 17 clutches of therizinosaurs eggs in that desert. The 100-million-year-old nest site contained numerous 5-inch round shells. The eggs may have already hatched since they contained only eggshells without embryos inside.

“Not only is this the largest colony of nonavian theropods, but this is the best-documented site,” said Kobayashi.

HuffPost noted that Kobayashi and his colleagues found the trove of fossilized eggs right next to their car in southeastern Mongolia in 2011.

“As the sun was setting, a guide pointed out an eggshell, and the team soon found one nest site right next to their car. Further investigation revealed four more nest sites. The following year, they returned and excavated a total of 17 clutches, for a total of about 75 eggs.”

The rare find suggested that Therizinosaurus may have been social, with parents guarding the eggs against predators. It’s is unclear if the dinosaurs formed herds or gathered only during a nesting season.

The fossil eggs would have had to be preserved quickly since otherwise they would have been gobbled up by a host of scavengers. Most likely, sediment buried the eggs through a sudden sandstorm, mudslide, or flood.


Therizinosaurus fossils were first discovered in 1948 by a team of Soviet and Mongolian paleontologists who at first thought the bones were those of a giant turtle. Russian paleontologist Evgeny Aleksandrovich Malayev wrote that the long arms were “powerful swimming organs” and that the claws were designed for “cutting aquatic vegetation.”

The forelimb skeleton wasn’t complete, so we don’t know its overall appearance or what it ate. It is thought that it may have had a small bird-like head and beak.

Over two decades later, scientists finally identified the incomplete fossil as a theropod with the longest claws of any animal in the history of the world. That’s why the Greek name translates to “Scythe lizard.”

Scientists believe these creatures from the late Cretaceous period (85-70 million years ago) could have nails as long as 1.5 meters long. There is as of yet no fossil evidence, but the dinos may have been covered in feathers like a huge, monstrous, horrifying bird. The feathers were not used for flight, but probably for warmth and to attract mates.

As menacing as those long claws appear, Therizinosaurus (probably) used them mostly to tear away at vegetation. A skull has not yet been found, but the Scythe lizard’s close relatives had small teeth built to munch on foliage. On the other hand, other therapods like the Tyrannosaurus rex were meat eaters, so the jury is still out.

The claws would definitely have made for effective defense weapons against large meat eaters. A clash of the titans that would have been epic, to say the least…

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