For centuries, scientists believed that spiders and their relatives evolved from land-dwelling ancestors. However, a new discovery of a 500-million-year-old fossil by researchers from the University of Arizona, Lycoming College, and King’s College London has revealed surprising similarities between ancient marine arthropods and modern-day arachnids.
The fossil, Mollisonia symmetrica, is believed to have lived in the ocean. Its central nervous system was imaged using light microscopy and showed an unexpected pattern of radiating neural centers, similar to that of spiders and scorpions. This finding suggests that these creatures may have started to diverge from other chelicerates long before they evolved into land-dwelling arachnids.
The researchers found that the unique nervous system in Mollisonia appears to be an inheritance from earlier ancestors, rather than a coincidence. If this theory is correct, it would place Mollisonia at the base of the arachnid lineage, making it a sister to horseshoe crabs and sea spiders.
This discovery challenges our understanding of spider evolution and may have implications for how we think about the origins of other complex features in these creatures. The study suggests that early arachnids on land may have driven the evolution of insects’ wings and flight, as well as the development of webs to catch prey.
Source: https://www.sciencealert.com/500-million-year-old-fossil-suggests-ocean-origin-for-spiders