Chinese scientists have unveiled the world's smallest known dinosaur eggs, shedding new light on the evolution of theropod dinosaurs during the Late Cretaceous period. The discovery, published recently in the scientific journal "Historical Biology," centers around a clutch of six remarkably well-preserved eggs found at a construction site in Ganzhou, southern China, in 2021.
Measuring just 2.9 centimeters in length—about the size of a cherry—the eggs have surpassed the previous record held by Himeoolithus murakamii. The prior record was an egg measuring approximately 4.5 centimeters found in Japan, belonging to a chicken-like dinosaur. The newfound eggs are significantly smaller, with an average length that is half that of a modern chicken egg.
The eggs are believed to belong to a new species of non-flying theropod dinosaurs, which researchers have named "Minioolithus ganzhouensis," after the city where they were discovered. According to geoscientist Rui Wu and colleagues, detailed analysis of the eggs' microstructures and likely limb bones within the eggs confirmed that they were not direct bird relatives but non-avian theropod dinosaurs instead.
Using advanced techniques such as scanning electron microscopy and electron backscatter diffraction, scientists were able to peer inside the eggs without damaging the delicate fossils. These tools revealed that the internal structure of the eggs remained almost completely intact, despite being over 80 million years old. The researchers noted unique characteristics, including small egg size, irregular egg arrangement, nodular and worm-like ornamentation on the shells, and a gradual boundary between two structural layers.
"In their paper, the researchers write, 'Minioolithus ganzhouensis is the smallest known dinosaur egg clutch till now and is significant for understanding the diversity of theropods in the Late Cretaceous,'" reported ScienceAlert.
The stone containing the eggs dates back to the Late Cretaceous period, approximately 80 million years ago. The irregular arrangement of the eggs has made it difficult for scientists to determine if all the eggs belonged to a single nest. However, the well-preserved state of the eggs has provided valuable insights into dinosaur reproduction and development.
The discovery is significant as it enhances our understanding of theropod evolution. Theropods were bipedal dinosaurs, often carnivorous, and included formidable predators like Tyrannosaurus rex. The small size of the eggs has led researchers to speculate about the reproductive strategies of these ancient creatures. It is possible that this species of dinosaur was small in size or perhaps belonged to a type that experienced rapid growth after hatching.
"There is great diversity in dinosaur eggs in terms of shape and size," noted Aljazeera. "This diversity does not always reflect the size of the dinosaur that laid the eggs." For example, some ornithopods, including duck-billed dinosaurs, laid eggs measuring 13.7 centimeters in length, while giant dinosaurs from the titanosaur group laid eggs not exceeding 15 centimeters, despite their enormous size.
Researchers believe that the variation in egg size among dinosaurs may be due to different reproductive strategies. The small size of the eggs may indicate a strategy of producing a large number of offspring or possibly a long period of care before hatching.
Fenglu Han, co-author of the study and paleontologist at the China University of Geosciences in Wuhan, said in a translated statement that future studies on these eggs could reveal more about the reproductive biology of Late Cretaceous theropod dinosaurs.
The findings have allowed researchers to place Minioolithus ganzhouensis within the theropod family tree, providing an important window into the history and diversity of dinosaurs during the Late Cretaceous period. Rui Wu and the team hope that further analysis of the discovery site will offer more clues about what laid these eggs and how these dinosaurs built their nests.
This discovery not only increases the diversity of known dinosaur eggs from the Late Cretaceous but also provides significant insights into the evolution of theropods. As the smallest known dinosaur eggs to date, the Ganzhou Mini Eggs offer a unique glimpse into the reproductive biology and development of non-avian theropod dinosaurs.
Sources: ScienceAlert, La Nacion, Aljazeera
This article was written in collaboration with generative AI company Alchemiq