World’s first preserved dinosaur sitting in the nest of eggs with fossilized babies

The fossil in question is that of an oviraptorosaur, a group of bird-like theropod dinosaurs that thrived during the Cretaceous period, the third and final period of the Mesozoic era (commonly known as the “age of the dinosaurs”). ) which extended from 145 66 million years ago. The new specimen was recovered from the oldest Cretaceous rocks, about 70 million years old, in Ganzhou City, Jiangxi Province, southern China.

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

The fossil consists of an incomplete skeleton of a large, presumably adult oviraptorid, crouched in a bird-like rearing posture on a clutch of at least 24 eggs. At least seven of these eggs retain bones or partial skeletons of unincubated oviraptorid embryos. The late stage of development of the embryos and the adult’s proximity to the eggs strongly suggest that the latter died at the time of incubating their nest, like their modern bird cousins, rather than laying eggs or simply guard the crocodile from the nest. style, as has sometimes been proposed for the few other oviraptorid skeletons that have been found above the nests.

“This type of discovery, essentially fossilized behavior, is the rarest of the rare ones in dinosaurs,” Dr. Lamanna explains. “Although some adult oviraptorids have previously been found in the nests of their eggs, no embryos have ever been found inside these eggs. In the new specimen, the babies were almost ready to hatch, which it tells us, without a doubt, that this oviraptorid had tended its nest for a long time. This dinosaur was a worried father who finally gave his life while caring for his young. “

The team also performed oxygen isotope analyzes indicating that the eggs were incubated at bird-like high temperatures, which added further support to the hypothesis that the adult died at the time of ‘incorporate the nest. In addition, although all embryos were well developed, some appear to have been more mature than others, which in turn suggests 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 specimen of oviraptorids is that the adult retains a cluster of pebbles in its abdominal region. These are almost certainly gastroliths, or “stomach stones,” rocks that would have been deliberately swallowed to help the dinosaur digest its food. This is the first time that undoubted gastrolites are found in an oviraptoride and therefore these stones may provide new insights into the diet of these animals.

Dr. Xu says, “It’s extraordinary to think how much biological information is captured only in this fossil. We’ll learn from this specimen for many years to come.”

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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 preserved on top of an embryo egg clutch sheds light on the reproductive biology of non-avian theropod dinosaurs. Science bulletin. 2020, https: //two.org /10.1016 /j.scib.2020.12.018.