Scientists have uncovered 518-million-year-old fossils in southwestern China that offer new clues about the evolutionary origins of starfish and their relatives. The fossils, named Yujingia glutenotunica, were discovered in the Maotianshan Shales in Yunnan Province, a site famous for preserving soft-bodied organisms that typically do not fossilize well. These fossils suggest that the last common ancestor of ambulacrarians—organisms that include starfish, sea urchins, and acorn worms—may have used tentacles to feed, rather than relying on gills to filter food, as previously thought. Yujingia glutenotunica measured between 8 and 22 millimeters in length and had a bottle-shaped body with tentacles extending from the upper part. The fossils preserve the body, gut, and appendages, making them rare examples of early ambulacrarians without a hardened skeleton. Some specimens show a U-shaped intestine, suggesting a complex digestive system. The animals had two types of appendages: one set of feather-like feeding tentacles that captured organic particles from the water, and a second set that may have helped them temporarily anchor to the seabed, though they may not have been highly mobile. This discovery challenges the long-held belief that the common ancestor of ambulacrarians was a worm-like creature that filtered food through its pharynx, like modern acorn worms. Instead, Yujingia suggests that this ancestor may have resembled starfish and their relatives, using tentacles for feeding. This finding could help explain why two closely related groups—starfish and their relatives, and chordates, which include humans—developed such different body structures over millions of years. Published in the journal Current Biology, the study used a detailed analysis of 505 morphological traits across 100 living and extinct species to determine Yujingia's evolutionary position. The results indicate that Yujingia is closer to the last common ancestor of modern ambulacrarians than previously known fossils, making it a key transitional form between early Cambrian tentacled animals and the groups that include hemichordates and echinoderms. The Maotianshan Shales are known for their exceptional preservation of soft-bodied organisms due to rapid burial in fine-grained, clay-rich sediments with low oxygen levels. This environment protected the organisms from scavengers and decomposers, allowing soft tissues to be preserved under favorable chemical conditions. Yujingia is considered to be very close to the last common ancestor of echinoderms, a group that includes starfish, sea urchins, and brittle stars. The evolution of hard, calcified skeletons in echinoderms is thought to have been a response to increased predation by other animals, such as arthropods, vertebrates, and mollusks. The study suggests that the different body forms and feeding strategies of echinoderms and chordates may have been shaped by their ecological roles. While echinoderms remained relatively fixed to the seafloor and specialized in feeding on particles, chordates evolved streamlined bodies and active movement to chase prey. This divergence in lifestyles may have led to the distinct body plans seen in these two groups today.