Exposed to incandescent light, coded fossil skulls are displayed on shaky iron shelves. Fossils of tortoises, rhinoceros horns and giant elephant-related mammals are piled up in obscure corners and corridors.
A warehouse for a paleozoological museum stores 30,000 fossils in Hezheng, an impoverished county in northwest China's Gansu Province.
Located in the Linxia basin on the joint zone of the Qinghai-Tibet Plateau and Loess Plateau, the county is often called the "kingdom of fossils."
The journey in preserving such an astonishing number of fossils started more than 30 years ago when a group of Chinese paleozoologists visited Hezheng.
Before that the treasures, once regarded as "dragon's bones," were used as an ingredient in a type of traditional Chinese medicine, and sold at a low price to medical companies in the 1950s.
Chen Shanqin, a fossil repair worker of the museum, looks after the fossils in Hezheng.
He looks more like a carpenter and spends most of the day in his workshop restoring the fossils. His 40 square-meter workshop is full of tools such as an electric saw, a grinder and steel nails.
Many of the tools are Chen and his team's own inventions, made of bike spokes, stitching awl and steel bars.
"Repairing fossils is not interesting or easy," said Chen, adding that some fossils are very fragile and easily broken into pieces. "It needs skill and patience."
Born in the 1960s to a rural family, Chen entered the field in 1986 and helped establish the museum, the only paleozoological museum in the country, in 2003.
After more than 30 years of surveying, researchers have collected over 30,000 specimens of ancient animal fossils, such as the Hipparion, an extinct genus of horse, and the Platybelodon, a large herbivore related to the elephant.
The museum claims that it holds six world records, including the largest and most of a particular type of fossil.
Although Hezheng is a poor county, the local government has invested more than 200 million yuan (around 29.7 million U.S. dollars) in building the museum, which has three pavilions and purchases fossils from private collectors.
In recent years, Hezheng has established a protection network involving volunteer guardians at village, township and county level. It also set up a geo-park to protect these ancient masters of the land.
However, owing to fund shortages the kingdom of fossils is encountering challenges.
"Fossils should be stored at fixed temperature and humidity, but now our storage warehouses are not qualified," Chen said.
In addition to improving the storage and display condition, He Wen, curator of the museum, suggested establishing a database to register the name and origin of fossil specimens found across the county.
He also said that collecting lost fossils specimens should receive more support.
As the value of fossils became known in the 1970s and 1980s, people secretly excavated them and sold them to medical companies. It is estimated that around 1,000 tonnes of "dragon bones" and "dragon teeth" were purchased from Hezheng during the period. Some fossils were even shipped overseas.
Li Tingdong, an academician with the Chinese Academy of Sciences, pointed out the value of the fossils.
He said the fossils provided solid information on ancient geography, climate, ecology and the Qinghai-Tibet Plateau uplift, as well as how every species emerges, develops, peaks and secedes.
Chen gets along well with these giant prehistoric creatures, knowing best their bodies and tempers. To know them, Chen explains, is to better understand ourselves, who will also become extinct one day.
"I am expecting more public participation in preserving the fossils," Chen said. "Only through knowing the principles of nature will people realize its message and be able to make decisions in the future."