Urokodia aequalis, an early Cambrian marine predator from the Chengjiang biota of China, preserves the earliest known evidence of chelicerae — the pincer-like structures that later evolved into the fangs of spiders and the pincers of scorpions. An artist’s impression of Urokodia aequalis, a marine predator that lived in the Cambrian seas around 518 million years ago. Image credit: Xiaodong Wang. Spiders, along with scorpions and ticks, form...
