A mysterious human skull found in the 1930s has been identified as an existing species after once being thought to be a new species all together, according to researchers.The studies posted in the journals Cell and Science have identified the 146,000-year-old skull known as "dragon man" has been categorized as a Denisovan.The researchers revealed that the Denisovans were discovered by their genomes and proteins to identify them.However, the reason it took so long to identify was that the attempts to extract DNA from a tooth failed.MYSTERIOUS 'DUMPED' BODIES OF WOMAN AND CHILD FOUND BY ARCHAEOLOGISTS IN PICTURESQUE TOWNResearchers also tried extracting DNA from the Harbin cranium as well, which also failed.When those methods failed, researchers turned to using dental calculus, which uses calcified dental plaque.The calcified dental plaque could hold and protect DNA due to its dense crystalline structure that resists degradation in various environments.EXPERTS SOLVE MYSTERY OF ANCIENT 'MUMMIFIED DRAGON' DISCOVERED BY JAPANESE SHOGUNResearchers used bleach on the dental plaque in order to eliminate any possible modern-day DNA.Once extracted, researchers began to compare the genetic material discovered to previous samples.The researchers found that the "dragon man" was not a new species but was a Denisovan and the very first intact specimen to date.According to the researchers, Denisovans coexisted with modern-day humans and are closely related to Neanderthals.The "dragon man" was discovered in mysterious circumstances when a Chinese laborer working on a bridge over the Songhua River found it.The man kept the Harbin cranium well hidden as he was instructed to hide it from the Japanese army.CLICK HERE TO GET THE FOX NEWS APPThe skull was donated shortly before his death in 2018, after which his family relocated the skull and gave it to the Geoscience Museum, Hebei GEO University professor Qiang Ji.While there are limitations to this study, the researchers said there is still so much to learn moving forward.It was called "dragon man" because it was found in the Heilongjiang province of China, which translates to Black Dragon River.Fox News Digitals Julia Musto contributed to this story.