Scientists have discovered two new feathered dinosaur species in northeastern China hidden in 125-million-year-old fossils.
The find sheds more light on the diversity of two-legged theropod dinosaurs that roamed China as well as the ecosystem they inhabited.
The two species, named Sinosauropteryx lingyuanensis and Huadanosaurus sinensis, both lived in China’s Jehol Biota – a region rich in well-preserved fossils of life forms that lived between 133 to 120 million years ago.
Huadanosaurus stood out among its close relatives with robust jaws and powerful neck muscles, which enabled it to efficiently hunt and kill mammals with its strong bite force, according to the study published in the journal National Science Review.
The dinosaur has been named after the Chinese word ‘Huadan’, meaning the birthday of a great person or a great institution, commemorating the 75th anniversary of the founding of the People’s Republic of China, and the Chinese Academy of Sciences.
Researchers also found the remains of two rodent-like mammals in the gut of this dinosaur’s fossil, which represents the first direct evidence of dinosaur-mammal predation in this ancient ecosystem.
“Huadanosaurus likely caught the small prey with its mouth, quickly killed its prey using the strong bite force of its maxillary teeth, and swallowed the prey whole during the hunt,” scientists wrote in the study.
The other dinosaur Sinosauropteryx lingyuanensis was only about 1.2 metres in length and likely preyed on birds.
It has been named after the Chinese city Lingyuan, where the fossils were found.
Although both the dinosaurs appear to have been similar sized, scientists say there was likely no competition between them as they had specialisations to hunt different prey items.
The feathers covering Sinosauropteryx likely served as a camouflage for the dinosaur to hide even under abundant direct sunlight in an open area, hinting it may have been active both in the day and night times.
Huadanosaurus, on the other hand, may have been nocturnal.
“In addition to differences in hunting style and prey, the active time of Sinosauropteryx may differ from Huadanosaurus,” scientists wrote.
Researchers have classified Sinosauropteryx into a distinct group of dinosaurs called Sinosauropterygidae, including the metre-long Sinosauropteryx prima and Sinocalliopteryx gigas, which grew to about 2.4 meters in length.
The findings point to the presence of diverse hunting styles among these small two-legged dinosaurs inhabiting this section of the Jehol Biota.
Such a unique composition of dinosaurs in this region hints at a lack of species exchange with other areas, scientists suspect.
This may have been due to geographic barriers created by the contraction and extension of the Earth’s crust, or because of sporadic volcanic eruptions, they say.
The formation of isolated rift basins also likely hindered species intermixing, they say.
These were small troughs caused by crust extension preceding the breakup of continents.
“This isolation prevented the ecosystem on the North China Craton from interacting with other areas during that time,” researchers write.
“The heightened selection pressure resulting from species competition in these isolated rift basins could have propelled the diversification of theropods,” scientists concluded.
