The claim is FALSE

Fossil found in China belongs to an aquatic reptile called Dinocephalosaurus orientalis.
→ The reptile lived during the Middle Triassic geological period. 

→ The 6-meter-long reptile is known for having a long neck and 32 vertebrae.
The publication of scientific research in the public domain and the dissemination of research results on social media can sometimes deviate from the aims of the research. Articles published in various fields such as medicine, psychology and archaeology can be taken out of context or distorted and shared on social media for "more engagement". Fact-checking of content that spreads in this direction has been done before. 

Fossil Found Belongs to a Water Reptile

When the image shared in the allegation is searched on search engines with the reverse image search method, it is found that the image is on the website Science News. According to the post on the site, the fossil found as a result of research by scientists from Germany, the United Kingdom and China belongs to an aquatic reptile named "Dinocephalosaurus orientalis" from the 'Middle Triassic' geological period in China.  
When Dinocephalosaurus orientalis is searched through search engines, the article published by the Transactions of the Royal Society of Edinburgh on February 23, 2024 is reached. In the article, the fossil found is considered one of the 7 best preserved specimens in the Guizhou region of China. The 240-million-year-old fossil is an aquatic, birthing, long-necked, 6-meter-long fossil with a long neck consisting of 32 vertebrae.

Conclusion;

The claim that a 240 million year old dragon fossil was found in China is false.