Paleontologists in China have unearthed the fossil of an oviraptorosaur perched on an egg nest. In itself, this is an amazing and rare discovery, but this fossil is unique in that the eggs still retain evidence of unbroken offspring. interior.
“It simply came to our notice then [non-avian] a dinosaur fossil known for keeping an adult skeleton on top of an egg clutch containing embryonic remains, “say the authors of a research paper published in the Science Bulletin. Found in China, the fossil extends our understanding of the behavior and physiology of oviraptorosaurs, while providing additional evidence that non-avian dinosaurs used bird-like behaviors.
Oviraptorosaurs, also known as oviraptors, have been named as such due to an early paleontological misunderstanding of similar fossils. The name means “egg thief”, but these dinosaurs were not thieves, as it was later shown that oviraptorosaurs were the rightful owners of fossilized eggs often found near their buried skeletal remains.
Indeed, fossils of oviraptorosaurs have previously been found nesting with their eggs. The novelty is that dino eggs still contain evidence of embryos inside. It is worth noting that the embryos in oviraptor eggs have been found before, but only in isolation. A famous example is “Baby Louie“Fossil, discovered in Henan, China, in the 1990s.
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Oviraptorosaurs were a highly successful Cretaceous theropod dinosaur. They varied greatly in size, with some of the largest weighing over 2,425 pounds (1,100 kilograms).). Common features include feathers, a long neck, wings and beaks. These non-avian dinosaurs looked very similar to birds, resembling modern ostriches. When nesting, these animals arranged their eggs in an almost perfect circle, layering their large egg claws in a remarkably orderly manner.
The new fossil described, named LDNHMF2008, was extracted from the Nanxiong Formation near the Ganzhou Railway in southern China’s Jiangxi Province. The fossil dates to the end of the Cretaceous period, about 70 million years ago. Preserves the remains of a medium-sized adult oviraptorosaur, lacking the skull and other skeletal features. The animal appears to have died while nesting.
These fossilized bones were found next to an “undisturbed clutch” of at least 24 eggs, “some of which are broken, exposing the embryonic bones,” the study’s authors wrote. Researchers led by Shundong Bi of Indiana University in Pennsylvania and Xing Xu of the Chinese Academy of Sciences have assigned eggs to fossil species. Macroolithus yaotunensis.
Oviraptorosaur nests that contain so many eggs at once are not uncommon and probably an adaptation to extreme poaching by real “egg thieves”.
Microscopic analysis of the fossils showed that some embryos were in the late stages of development and were about to hatch. The authors saw this as potential evidence that oviraptors were actively incubating their nests and not just guarding them, as some paleontologists have speculated.
“In the new specimen, the babies were almost ready to hatch, which no doubt tells us that this oviraptorid had cared for its nest for a long time,” said Matthew Lamanna, a paleontologist at the Carnegie Museum of Natural History and co-author of the new study. in a statement. “This dinosaur was a caring parent who eventually gave his life while caring for his cubs.”
Other evidence asserted this interpretation, namely an analysis of oxygen isotopes that showed that the eggs were incubated at high temperatures, similar to birds, around 97 to 100 degrees Fahrenheit (36 to 38 degrees Celsius). Interestingly, the eggs were found in different stages of development, which means that they hatched at different times. This is called hatching asynchrony, a reproductive phenomenon seen in modern birds. The authors could not attribute a cause to asynchronous hatching, but presented a plausible scenario, as they write in their study:
“As in ostriches, oviraptorosaurs would have started incubating the nest only after all the eggs had been laid, so that the lower eggs, which had been laid earlier, would have been incubated in proportion to the same period of time as the upper eggs. However, the upper eggs would have hatched earlier than the lower eggs, because being closer to the brooding adult would have received more heat from this individual than the lower eggs, and thus the embryos in them would have hatched. be developed faster. ”
Finally, the scientists also detected a handful of pebbles in the abdominal region of the dino. These rocks are probably gastrolites, which animals swallow to aid digestion. It is the first time such a thing is documented in an oviraptorosaur and a potential clue in their diets. It is, of course, a ton of new perspectives for a single fossil, though remarkable.
“It’s amazing to think how much biological information is captured in this single fossil,” Xu said. “We will learn from this specimen for many years to come.”