The world’s first preserved dinosaur perched on a nest of eggs with fossilized babies

The fossil in question is that of an oviraptorosaur, a group of theropod dinosaurs resembling birds that flourished in the Cretaceous, the third and final period of the Mesozoic era (commonly known as the “Age of Dinosaurs”), which has expanded since at 145 by 66 million years ago. The new specimen was recovered from the oldest Cretaceous rocks, about 70 million years old, in the city of Ganzhou in Jiangxi Province in southern China.

“Dinosaurs preserved in nests are rare, as are fossil embryos. This is the first time a non-avian dinosaur has been found, perched on an egg nest that holds embryos, in a single spectacular specimen,” explains Dr. Shundong Bi. .

The fossil consists of an incomplete skeleton of a large oviraptorid, probably an adult, crouched in a bird-like posture above a clutch of at least 24 eggs. At least seven of these eggs keep the bones or partial skeletons of oviraptorid embryos without hatching. The late stage of embryo development and the close proximity of the adult to the eggs strongly suggest that the latter died in the act of incubating its nest, like its modern cousins ​​of birds, rather than laying its eggs or simply simple to guard the nest crocodile – style, as sometimes proposed for the other few oviraptorid skeletons that were found at the top of the nests.

“This type of discovery, in essence, fossilized behavior, is the rarest of the rare in dinosaurs,” explains Dr. Lamanna. “Although several adult oviraptorids have been found in the nests of their eggs before, no embryos have ever been found inside these eggs. In the new specimen, the babies were almost ready to hatch, which no doubt tells us that this oviraptorid tended to nest for a long time. This dinosaur was a caring parent who eventually gave his life while caring for his cubs. “

The team also performed oxygen isotope analyzes indicating that the eggs were incubated at high bird-like temperatures, adding additional support to the hypothesis that the adult perished in the act of hatching its nest. Moreover, although all embryos were well developed, some appear to have been more mature than others, suggesting that oviraptorid eggs in the same clutch may have hatched at slightly different times. This feature, known as asynchronous hatching, appears to have evolved independently in oviraptorids and some modern birds.

Another interesting aspect of the new oviraptorid specimen is that the adult keeps a group of pebbles in its abdominal region. These are almost certainly gastrolites, or “stomach stones,” rocks that would have been deliberately swallowed to help the dinosaur digest its food. It is the first time that gastroliths have undoubtedly been found in an oviraptorid and, as such, these stones can offer new perspectives on the diet of these animals.

Says Dr. Xu: “It’s amazing to think about how much biological information is captured in this single fossil alone. We will learn from this specimen for many years to come. “

###

See the article:

Bi, S., Amiot, R., de Fabrègues, CP, Pittman, M., Lamanna, MC, Yu, Y., Yu, C., Yang, T., Zhang, S., Zhao, Q. and Xu , X., 2020. An oviraptorid kept above an embryonic egg clutch sheds light on the reproductive biology of non-avian theropod dinosaurs. The scientific bulletin. 2020, https: //two.org /10.1016 /j.scib.2020.12.018.