Description and Classification

Yulong was a relatively small dinosaur, especially since the known specimens are juveniles. These young dinosaurs were likely about 0.5 meters (1.6 feet) long. Like other oviraptorids, Yulong would have had a beak-like snout without teeth, and its body was probably covered in feathers. It walked on two legs and had arms that were shorter than its legs. Although the known fossils are of young animals, scientists can tell that Yulong had a low crest on its skull, which might have become more prominent as it grew older.

Yulong belongs to the family Oviraptoridae, a group of bird-like theropod dinosaurs. This family includes other famous dinosaurs such as Oviraptor and Citipati. Oviraptorids are known for their strange-looking skulls, often with crests, and their parental care behavior, as some have been found fossilized sitting on nests of eggs. Yulong is one of the smallest known members of this group.

Distinguishing Features

Key features that help identify Yulong include:

• Small size, particularly based on the juvenile specimens found.
• A short, beak-like, toothless snout, typical of oviraptorids.
• The presence of a low bony crest on top of its skull, even in young individuals.
• Likely covered in feathers, similar to its close relatives.
• Relatively long legs compared to its body size, suggesting it was a nimble runner.

Paleoenvironment and Diet

Yulong lived in what is now Henan Province in China during the very end of the Cretaceous period. The environment of the Qiupa Formation at that time was likely a warm and relatively humid landscape with rivers, lakes, and floodplains. Yulong shared this habitat with other dinosaurs, including other theropods like the dromaeosaurid Luanchuanraptor and the ornithomimosaur Qiupalong, as well as various hadrosaurids (duck-billed dinosaurs) and ankylosaurs.

The exact diet of Yulong is not known for certain, but like other oviraptorids, it was probably an omnivore. Its strong beak could have been used to crush seeds, nuts, and hard-shelled invertebrates like insects or mollusks. It might have also eaten small vertebrates or eggs. The variety of possible food sources suggests it was an adaptable feeder.

Significance and Ongoing Research

The discovery of Yulong is significant because multiple well-preserved skeletons of young individuals were found. This allows paleontologists to study how oviraptorid dinosaurs grew and changed from youth to adulthood, a field known as ontogeny. Finding several specimens together might also suggest that young Yulong lived in groups or that these were from a nesting site. Yulong adds to the rich diversity of oviraptorid dinosaurs known from Asia, particularly from the Late Cretaceous period.

Ongoing research on Yulong focuses on understanding its growth patterns by comparing the different juvenile skeletons. Scientists study the microscopic structure of its bones (bone histology) to learn about its growth rate and age. Comparing Yulong with other juvenile and adult oviraptorids helps to refine our understanding of the evolutionary relationships and developmental changes within this fascinating group of dinosaurs. These fossils also provide valuable information about the ecosystem of the Qiupa Formation just before the mass extinction event that wiped out the non-avian dinosaurs.