Scientists in Northeast China have made a groundbreaking discovery by identifying two new species of dinosaurs, named Sinosauropteryx lingyuanensis and Huadanosaurus sinensis. These findings contribute significantly to our understanding of the evolution of small, feathered theropods and highlight the extensive diversity found in the 125-million-year-old Jehol Biota, as reported in the National Science Review.

the fossil of Huadanosaurus sinensis contained remnants of two mammals, which marks the first definitive evidence of predation between dinosaurs and mammals in this ancient ecosystem. According to Qiu Rui, the lead author and associate researcher at the Natural History Museum of China, the anatomy of Huadanosaurus, including its robust jaws and muscular neck, suggests it was capable of delivering a powerful bite that allowed it to hunt mammals effectively.

In this study, the scientists noted that Huadanosaurus' predatory behavior was quite distinct from that of its relatives, such as Sinosauropteryx prima and Sinocalliopteryx gigas. The former primarily fed on lizards and was about one meter long, while the latter grew to 2.4 meters and preyed on dromaeosaurs. This difference in hunting strategies among members of the same dinosaur lineage is regarded as particularly unusual.

Moreover, the classification of these feathered dinosaurs was revised, with Sinosauropterygidae designated as a distinct group rather than being categorized under Compsognathidae, which is now considered misleading. Wang Xiaolin, a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, explained that an analysis of 504 theropod species reveals that Jehol's sinosauropterygids represent a unique lineage located at the base of Coelurosauria.

The study connected the diversification of these dinosaurs to significant tectonic changes that took place 125 million years ago when the North China Craton was devastated, leading to the formation of isolated rift basins. Zhou Zhonghe, an IVPP researcher, highlighted that in typical Mesozoic ecosystems, a single dinosaur lineage often occupied a specific ecological niche. However, in Liaoning, multiple hunting strategies emerged within the sinosauropterygids, while distantly related species like dromaeosaurs and tyrannosaurs exhibited overlapping ecological roles.

This concept of "diversification within lineages, and competition between lineages" helps explain the incredible diversity observed within the Jehol Biota, which surpasses other known dinosaur ecosystems. The findings shed light on the important contribution of China's fossil-rich areas to the understanding of our planet's evolutionary history. The research was conducted with the support of the National Natural Science Foundation of China and the Chinese Academy of Sciences.