Inside the fossil dinosaur egg is a well-preserved embryo

A rare appearance inside a fossil dinosaur egg found in southern China reveals a neatly preserved embryo – and some of these prehistoric creatures claim to be more common with modern birds than previously thought.

Scientists say the embryo inside the egg, which was laid 72 million to 66 million years ago during the Cretaceous, was the embryo of a two-legged, feathered carnivore called the oviporotoride. They said, in Essay on Discovery Published in iScience magazine on Tuesday, the embryonic curved body position — the blunt tip of a 7-inch-long egg with its back and its head between its legs — resembles bird embryos.

“This pose has never been recognized by any dinosaur embryo before. The pose suggests that the embryo took a nesting position before hatching – which was previously considered unique to birds,” said Fionn Weiss Ma, a backbone archaeologist and co-author of the study at the University of Birmingham in the UK.

He called the newly described model “one of the best preserved dinosaur nuclei ever discovered”.

In birds, the tucking embryo leaves its right wing above its head and its crane moves towards the air at the blunt end of the egg. That orientation helps to move the head of the brooding chick because it uses its hook to break the egg hole and come out.

Oviroptorite embryo found in southern China.


Photo:

Jing et al., 2021

“Failure to achieve this posture will increase the chances of death because the chances of the bird successfully breaking the egg are low,” Ms Ma said.

Researchers also say that cats need to be included in any precautionary measures against the virus.

This specimen is one of several fossils discovered in the Chinese city of Kanzhou two decades ago, but was not recognized as a fossil dinosaur egg until 2015 when evaluated by an expert. Careful examination of one of the eggs, which turned to fossil after rupture, showed that it contained a preserved oviproperid embryo.

Ancient researchers often used computed tomography or CT to examine the interiors of fossils. But when researchers scanned the fossil embryo, “the results were not great,” Ms Ma said. So the scientists carefully observed this pattern and then created a luminous reconstruction of the embryo inside the egg.

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Fossilized dinosaur eggs have been discovered over the past century and a half. But embryonic eggs are rare because the bones of embryonic dinosaurs are so fragile that they are often destroyed before the fossilization process is complete.

A nucleus like the one described in the paper, with all its bones in place, is still rare. Dinosaur nuclei are usually found with their bones deformed or unattached, making it difficult to reconstruct their anatomy and pre-hatching behavior.

Oviroptorites, a group of dinosaurs whose name means “egg thief”, has no teeth, but curved cranes suitable for eating eggs and shellfish. Animals – some the size of turkeys and others 23 feet long – were abundant in Asia and North America about 125 million to 70 million years ago.

Animals belong to a group Two-legged, three-legged dinosaurs called theropods. All modern birds can find their appearance in therapods, and according to ancient researchers features such as feathers, two legs and laying eggs are common to both groups.

Jasmina Wyman, a paleontologist at the California Institute of Technology who did not participate in the study, called the new discovery a “very attractive observation” because the elongated eggs of oviproptor dinosaurs differ significantly in shape from those of any other bird.

But this discovery alone is not enough, said Shundong B, a biologist at Indiana University in Pennsylvania and co-author of a study on fossil oviropod found in China. Its eggs. The study was published in March In the journal Science Bulletin.

“The conclusion about ducking ‘behavior is debatable because it is primarily based on a model,” said Dr. P., who is not involved in the new research.

Ms. Ma is hopeful that similar models will be found.

“Many dinosaur embryos like this can be found,” he said. “It’s a matter of time and luck. With more fossils, we can study the development and behavior of baby dinosaurs in more detail and with stronger evidence.

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