Researchers named the dinosaur Wulong bohaiensis, which translates to "a dancing dragon."
The dinosaur was about the size of a raven but double its length with a long, bony tail. Its entire body was covered with feathers, complete with two plumes at the tail's end.
Despite its small size, it had a fierce, narrow face and a mouth full of sharp teeth. Like a bird, it had small, light bones and wing-like forelimbs. And there were also a number of feathers on its legs.
The fossil was initially discovered in the fossil-filled Jehol Province a decade ago by a farmer and was placed in China's Dalian Natural History Museum.
Researchers, including Ashley Poust, a postdoctoral researcher at the San Diego Natural History Museum, later analyzed the fossil (at the time, Poust was still a student at Montana State University).
"The new dinosaur fits in with an incredible [range] of feathered, winged animals that are closely related to the origin of birds," Poust, the study's author, said. "Studying specimens like this not only shows us the sometimes surprising paths that ancient life has taken, but also allows us to test ideas about how important bird characteristics, including flight, arose in the distant past."
This dinosaur was a juvenile when it died, according to its bones, but its feathers resembled that of a mature adult. This suggests that the feathers grew quickly, unlike modern birds, which take time to grow their mature feathers.
"Either the young dinosaurs needed these tail feathers for some function we don't know about, or they were growing their feathers really differently from most living birds," Poust said.
The dinosaur was an early relative of Velociraptors, which lived 75 million years ago. Its contemporaries would have been Microraptors, small feathered dinosaurs that resembled birds.
The researchers actually sliced into several bones from the fossil and studied them with microscopes to understand the different regions of the skeleton. They also compared it to a close relative that also appeared more mature, known as the Sinornithosaurus.
Surprisingly, that dinosaur was also still growing when it died. The researchers said that histology, or cutting up the bones, was the only way for them to truly know the life stage of the dinosaurs when they died.
"We're talking about animals that lived twice as long ago as T. rex, so it's pretty amazing how well-preserved they are," Poust said. "It's really very exciting to see inside these animals for the first time."
Fossils from the Jehol Province have painted a portrait of the diverse life that once flourished there. It's an area in northeastern China full of exceptionally preserved fossil discoveries that has been studied for the past 90 years.
Researchers learned that birds, pterosaurs and bird-like dinosaurs all lived in the environment at the same time. This is also when flowering plants initially began to flourish.
"There was a lot of flying, gliding and flapping around these ancient lakes," Poust said. "As we continue to discover more about the diversity of these small animals, it becomes interesting how they all might have fit into the ecosystem. It was an alien world, but with some of the earliest feathers and earliest flowers, it would have been a pretty one."