An embryo between 66 and 72 million years old in a fossilized dinosaur egg is shedding new light on the link between the behavior of modern birds and dinosaurs.
The fetus, nicknamed “Baby Yingliang”, was discovered in rocks of the Upper Cretaceous period in Ganzhou, southern China, and belongs to Toothless theropod dinosaur or oviraptorosaurus.
The fossil, one of the most complete dinosaur embryos ever found, indicates that these dinosaurs developed similar postures to near-hatching birds. The result is presented in Science.
The scientists, led by researchers from the University of Birmingham (UK) and the Chinese University of Geosciences (Beijing), found that the ‘Baby Yingliang’ pose is unique among known dinosaur embryos: its head sits under the body and the feet are on either side. It spiraled along the sharp end of the egg. This position, which was hitherto unknown in dinosaurs, is similar to that of modern bird embryos.
In modern birds, these poses are associated with “tuck,” a behavior controlled by the central nervous system that is critical to successful hatching. After studying the egg and embryo, researchers believe that this pre-hatching behavior, hitherto considered unique to birds, may have originated among non-avian theropods.
The fetus is expressed in its position in life without significant changes due to ossification. It is 27 cm long from head to tail, and the organism is located inside a 17 cm long egg. The specimen is in the Yingliang Stone Museum of Natural History.
“Dinosaur embryos are among the rarest and most incomplete with dislocated bones,” explains Fion Waisum Ma, co-author and PhD researcher at the University of Birmingham. “We are very excited about the discovery of ‘Baby Yingliang,'” he said in a statement, saying that it has been preserved in great condition and helps us answer many From questions about the growth and reproduction of dinosaurs with it.
“It is interesting to see that this dinosaur embryo and the chicken embryo are similarly formed inside the egg, which may indicate similar behaviors before hatching,” he adds.
‘Baby Yingliang’ has been identified as an oviraptorosaur based on its deep, toothless skull. Oviraptorosaurs are a group of feathered theropod dinosaurs, closely related to modern birds, known from the Cretaceous period of Asia and North America.
It is likely that their beak shapes and changing body sizes allowed them to adopt a wide variety of diets, including herbivores, grouse, and carnivores.
Birds have been known to develop a series of bending poses, bending their bodies and putting their heads under their wings, shortly before hatching. Fetuses that do not reach these positions are more likely to die because they were not born.
By comparing ‘Babé Yingliang’ to other theropods, dinosaurs and long-necked sauropods, the team suggested that tuck behavior, once considered unique to birds, first evolved in theropods tens or hundreds of millions of dinosaurs. years. Additional discoveries of embryo fossils will be invaluable in further testing this hypothesis.
Study co-author Professor Lida Sheng from China University of Geosciences (Beijing) explains “This dinosaur embryo was obtained by Yingliang Collection Director Liang Liu as a suspected egg fossil around 2000.
During the construction of the Yingliang Stone Museum of Natural History in 2010, Museum staff inspected the repository and discovered specimens that had been identified as fossilized dinosaur eggs.Fossils were prepared and the embryo hidden inside the egg was discovered. This is how ‘Baby Yingliang’ came about.
Professor Steve Brusatte of the University of Edinburgh, who is part of the research team, adds this “This dinosaur embryo inside its egg is one of the most beautiful fossils I have ever seen. This tiny prenatal dinosaur resembles a little bird wrapped in its egg, and is more evidence than many of the distinguishing features of today’s birds that first evolved into our ancestors’ dinosaur,” he said.
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