Scientists digging through old fossils have identified a 520-million-year-old mega-claw with an almost completely preserved nervous system—the oldest such find ever, the LA Times reports. The specimen belongs to the Alalcomenaeus family, which is part of a larger group of "megacheirans," meaning roughly "mega-claw" or "great appendage." These creatures were notable for the claw-like limbs growing out of their heads; this particular creature was just an inch long. The specimen, found in the Yunnan Key Laboratory in China, mysteriously had iron deposits in its nervous system, making it easy to image.
"We have no idea why" the iron was there, the lead researcher says. "It is helpful for our research, but we are really mystified." Researchers were hoping brain imaging could shed light on the creature's evolutionary lineage, specifically when crustaceans, like crabs and lobsters, became distinct from chelicerates, like horseshoe crabs, scorpions, and spiders. They found that the specimen's brain was distinct from a 520-million-year-old crustacean discovered there last year, indicating that the two groups were already distinct at that time, and their common ancestor must be even older, CNN explains.