A stunning fossil egg has enabled paleontologists to find new clues about the early evolution of a dinosaur

Riley Black

The little dinosaur was almost ready to hatch. Nestled in its elongated egg, the beak-shaped, almost parrot-like Oviraptorosaur curled up in a C-shape with its head tucked between its arms and legs. This was not an accidental pose as the dinosaur was approaching a day of breeding that would never come. Modern birds adopt the same pose in their eggs, a very ancient behavior that helps birds emerge from their eggs and that dates back over 66 million years.

Figuring out how dinosaurs grew in their eggs was for paleontologists a challenging job. Well-preserved fossil eggs are rare, and fossil eggs with delicate, embryonic dinosaurs inside are even rarer. But the discovery of an exquisite oviraptorosaur embryo called YLSNHM01266 has given paleontologists a delicate and detailed look at what some baby dinosaurs were doing in their eggs as they prepared for the outbreak, and this find could help experts make similar finds better to understand.

The intricate fossil that University of Birmingham paleontologist Waisum Ma and his colleagues described today in iScience was discovered about 20 years ago in Ganzhou, China. At first it wasn’t even clear that the fossil was an egg at all, but it was still bought by Liang Lu of the Yingliang Group stone company. The egg waited in storage for years until the construction of the Yingliang Stone Nature History Museum prompted museum staff to take another look around. Not only was the fossil an egg, Ma says, but cracks in the shell also revealed tiny bones inside. When skilled taxidermists scraped off the outer shell, they found one of the best-preserved dinosaur embryos ever seen.

“I was very surprised to see this dinosaur embryo,” says mom. Often times, dinosaur embryos are either incomplete or preserved as a jumble of tiny bones in their shells. Instead, YLSNHM01266 is complete from snout to tail, the hole cut in the egg by fossil taxidermists that literally serves as a window to see how the little dinosaur grew up.

The dinosaur inside is an oviraptorosaur. These feathered, omnivorous dinosaurs had beak faces and often ornate coats of arms on their heads. Ironically, it was believed that the first Oviraptorosaur ever described – Oviraptor itself – was caught robbing a nest because of its association with eggs. Finds since then have revised the image of the dinosaur. Several Oviraptorosaurs, and likely Oviraptor itself, have been found sitting on their nests and may have been some of the most observant dinosaur parents. “We learn so much about oviraptorosaur eggs that it’s hard not to get excited,” says University of Edinburgh paleontologist Gregory Funston, who was not involved in the new study. “We now know their nesting patterns, breeding habits, eggshell color and some fine details of how their embryos developed” He adds what gives a lot of information to compare with other dinosaurs – both our non-avian favorites from the prehistoric past and the birds we see around us today.

But that’s not all the conservation of the tiny oviraptorosaur does him remarkable. The attitude of the dinosaur tells paleontologists something new about the evolution of these dinosaurs. The fossil is the ancient equivalent of a “tucking”? Keeping birds such as chickens. “In the stowed position, the head is under the right wing with the body curled up” tells Ma what happens in the days before they hatch. It’s not a fluke, but a pose that helps stabilize the head when birds push and peck out of the eggshell, meaning oviraptorosaurs likely did the same.

â € œI think the authors deliver a strong one Argument for their interpretationâ ???? says Funston. While other oviraptorosaur embryos are incomplete or sometimes even damaged by the way they were obtained or prepared, the new fossil is exceptional and can serve as a “Rosetta Stone”. for other oviraptorosaur embryos.

Not all dinosaurs hatched in the same way. The long-necked, herbivorous sauropod dinosaurs – like Brachiosaurus and its relatives – usually had round eggs and were not as bird-like in development. For example, a recently discovered sauropod embryo had a horn-like protrusion on its snout that helped it pierce and push the egg out of it, much like crocodiles and lizards did. And even today some flightless birds like emus emerge from their eggs. But the oviraptorosaur egg suggests that these dinosaurs share at least some important traits in common with birds, and that a myriad of features that set modern birds apart, such as feathers, a wishbone, and colored eggs that differ. were inherited from much older dinosaurs. Finding these links between prehistory and modern times can help paleontologists better understand the lives of extinct dinosaurs that we will never see in person.

“We currently know little about pre-hatch behavior in theropod dinosaurs . ”Ma says, but knowing that oviraptorosaurs evolved like many modern birds allows experts to look at other embryos and estimate how long they evolved. The little dinosaur in the egg, for example, corresponds to what domestic chickens do in the egg on day 17. If the Cretaceous dinosaur grew at the same rate, it would be about three days after hatching when it was buried.

The task now is to find and identify more dinosaur embryos. If YLSNHM01266 has been in storage for years, there may be others. “Ideally, we need to find more oviraptorid embryos to really figure out their developmental pattern” says study co-author Darla Zelenitsky, “but we’re definitely starting to put the pieces of the puzzle together.”

Riley Black
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Riley Black is a freelance science writer specializing in evolution, paleontology, and natural history who regularly blogs for Scientific American.

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