Over 500 million years ago, a small hunter lived in the warm oceans of what is now southern China. This ancient marine animal, named Urokodia, was only about three centimeters wide. It had large eyes on stalks and a body with many parts. Scientists have now found that Urokodia is the oldest known creature with the basic features for spider fangs.
The discovery, published in the journal Nature, used advanced technology. A team from China's Yunnan University and the UK's University of Leicester used X-ray tomography, similar to a CT scan, to examine the fossil. This method allowed them to create a 3D model without damaging the fossil.
Inside the fossil, they discovered something amazing. The rock had preserved the animal's soft tissues for millions of years. The X-rays showed a pair of small, claw-shaped limbs in front of Urokodia's eyes. Professor Yu Liu, who led the study, said they immediately knew it was an exciting find and a distant ancestor of animals like scorpions and spiders.
These small claws are early versions of chelicerae, which are front limbs modern animals use to catch and eat food. This group of animals, including spiders, scorpions, and ticks, has over 100,000 species today.
Before this discovery, the oldest known animal with these structures lived 14 million years after Urokodia. These new findings help explain the evolution from early arthropod legs to the specialized pincers and fangs of later animals.
The fossil was found at the Chengjiang site in Yunnan Province, known for preserving ancient soft-bodied animals. This site has shown evidence of rapid biological development during the early Cambrian Period. Professor Mark Williams of the University of Leicester noted that Urokodia was part of a diverse ancient ecosystem. He stated that these fossils offer important insights into how life evolved on Earth.