China: discovery of an exceptional dinosaur fossil resting on its nest filled with eggs

A rare pearl straight from the Cretaceous period. This is the discovery that scientists have just announced in a study published by the journal Scientific Bulletin. During excavations in Jiangxi province in southern China, they unearthed the exceptional remains of a dinosaur still sitting on its nest.

This type of discovery is one of the rarest in dinosaursCarnegie Museum of Natural History (CMNH) paleontologist Dr Matt Lamanna said in a statement. of their owner.

However, this is precisely the case here. Because the dinosaur is not alone. In its nest, there are about twenty eggs, some of which contain fossilized embryos. In recent decades, many nests have already been excavated, often with eggs, sometimes with the parent still sitting on them.

An oviraptorosaur and its future young

Nevertheless, it is much rarer that fossilized embryos are still found there. “It is the first time that a non-avian dinosaur has been discovered, sitting on a nest of eggs with preserved embryos, in a single spectacular specimenSaid Dr. Shundong Bi, professor at Indiana University in Pennsylvania.

According to the study, the incomplete skeleton would belong to an oviraptorosaur, a group of theropod dinosaurs that lived in the Cretaceous period, 145 and 66 million years ago. Specifically, the specimen is believed to be part of the Oviraptoridae subgroup, feathered ostrich-like theropods that evolved in Asia, particularly China.

Estimates indicate that the current fossil dates back around 70 million years. The adult skeleton is in a squatting position, like a brooding bird, and tops at least 24 eggs. Seven of them contain partial bones or embryonic skeletons.

The scene testifies to the close proximity between the adult and its future young and provides valuable information on the behavior of this oviraptorid. With nest fossils, it’s usually difficult to tell if the parent was laying their eggs, protecting them from possible threat, or patiently incubating them when they died.

In this case, however, paleontologists lean towards the latter option. Analyzes performed on the eggs revealed that they were at a relatively advanced stage of development and that they were incubated at a high temperature, similar to that of the adult body, between 30 and 38 ° C.

In this specimen, the babies were almost ready to hatch, which tells us without a doubt that this oviraptorid had been brooding its nest for some time. This dinosaur was a caring parent who ended up giving his life to support his cubsSaid Dr Lamanna, co-author of the report.

Another interesting detail, the analyzes revealed that some embryos seemed more mature than others. This observation suggests that all eggs in the same clutch might hatch at slightly different intervals. A characteristic called “asynchronous hatching” which is already known in some modern birds.

It is possible that this difference is related to the fact that oviraptorosaurs did not wait until they had laid all of their eggs before starting to hatch them. But it’s also possible that it was simply the position of certain eggs, closer to their parent, that resulted in faster development. Difficult to decide at the moment.

Likewise, it is not known whether the adult was male or female. Some data support the first hypothesis, which could confirm previous studies suggesting the involvement of the father in the brooding of theropods. In some modern birds like the ostrich, the parents take turns hatching the eggs.

These results demonstrate that the evolution of reproductive biology within the archosaur lineage (which includes non-avian dinosaurs but also birds, editor’s note) was more of a complex process than a linear and incremental process“, Write the authors in their report.

Besides reproductive behavior, the fossil also provided information about the specimen’s diet. The researchers discovered, in his abdominal region, the presence of a set of stones. They think they are gastroliths, “stomach stones” that are intentionally swallowed to aid digestion.

According to the study authors, this is the first time that such gastroliths have been detected in an oviraptorid. “It’s amazing to think of all this biological information captured in a fossilSaid Dr Xing Xu, paleontologist from the Institute of Vertebrate Paleontology and Paleoanthropology.