Paleontologists in China have excavated the fossil of an oviraptorosaurus perched on a nest of eggs. In itself it is a wonderful and rare discovery, but this fossil is unique in that the eggs still preserve evidence of the unbroken offspring. within.
‘Here we report the first [non-avian] dinosaur fossil known to contain an adult skeleton on top of an egg clutch containing embryonic remains, ‘the authors of a research paper published in Science Bulletin. The fossil, found in China, expands our understanding of oviraptorosaurus behavior and physiology, while further proving that dinosaurs not used by birds have bird-like breeding behavior.
Oviraptorosaurs, also known as oviraptors, were 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 next to their buried skeletal remains.
Indeed, fossils of oviraptorosaurs with their eggs have been found before. What is new here is that the dino eggs still contain evidence of the embryos inside. It is worth noting that embryos in oviraptor eggs have been found before, but only in isolation. A well-known example is the ‘Baba LouieFossil, discovered in the 1990s in Henan, China.
G / O Media can get a commission
Oviraptorosaurs were an extremely successful theropod dinosaur of the Cretaceous. They varied greatly, with some of the largest weighing 1100 kilograms). Common features include feathers, a long neck, wings and beaks. These non-bird dinos looked very bird-like, like modern ostriches. At the nest, these animals arranged their eggs in an almost perfect circle and laid their large clawed eggs in a remarkably orderly manner.
The newly described fossil, designated LDNHMF2008, was extracted from the Nanxiong Formation near the Ganzhou Railway in Jiangxi Province in southern China. The fossil dates to the end of the Cretaceous, about 70 million years ago. It preserves the remains of an adult medium-sized oviraptorosaurus, with its skull and other skeleton skeleton. The animal appears to have died while in a nesting position.
These fossilized bones were found next to an ‘undisturbed clutch’ of at least 24 eggs, ‘some of which are broken, exposing embryonic bones’, the authors wrote in the study. The researchers, led by Shundong Bi of Indiana University of Pennsylvania and Xing Xu of the Chinese Academy of Sciences, awarded the eggs to the fossil species. Macroolithus yaotunensis.
Oviraptorosaur nests containing so many eggs at once are not uncommon, and are 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 see this as possible evidence that oviraptors are actively incubating their nests and not just protecting them, as some paleontologists have speculated.
“In the new specimen, the babies were almost ready to hatch, which undoubtedly tells us that this oviraptorid has long cared for its nest,” said Matthew Lamanna, a paleontologist at the Carnegie Museum of Natural History and co-author. of the new study, said in a statement. “This dinosaur was a caring parent who eventually gave his life while raising his young.”
Other evidence confirms this interpretation, namely an oxygen isotope analysis showing that the eggs were incubated at high, bird-like temperatures between 97 and 100 degrees Fahrenheit (36 to 38 degrees Celsius). Interestingly, the eggs were found to be in different stages of development, which means that they hatched at different times. It is referred to as hatch asynchrony, a reproductive phenomenon seen in modern birds. The authors could not attribute a cause to the asynchronous hatching, but they presented a plausible scenario, as they write in their study:
‘As with ostriches, oviraptorosaurs would only begin incubating the nest after all eggs have been laid, so that the lower eggs, which were laid earlier, would incubate as much time as the upper eggs. However, the upper eggs would have hatched earlier than the lower eggs because, closer to the hatching adult, they would have received more heat from this individual than the lower eggs, and thus the embryos would have developed faster. ‘
Eventually, the scientists also found a handful of pebbles in the abdominal region of the dino. These rocks are probably gastrolytes, which swallow animals to aid digestion. This is the first time such a thing has been documented in an oviraptorosaurus, and a possible clue in their diet. Admittedly, this is a lot of new insight for a single, albeit remarkable, fossil.
“It’s extraordinary to think how much biological information is just captured in this single fossil,” Xu said. “We’ll be learning from this copy for many years to come.”