Ancient fossils redefine starfish origins
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An international team of scientists studying 518-million-year-old fossils in southwestern China discovered Yujingia glutenotunica, an animal that lived during the Cambrian explosion.
This creature provides new insight into the evolutionary history of ambulacrarians, the group including starfish, sea urchins, and acorn worms. The fossils reveal Yujingia used featherlike tentacles to capture food from the water, challenging previous theories that its ancestors filtered food passively.
Researchers from the University of Cambridge and Northwest University in China analysed the fossils, measuring them between 8 and 22 millimeters long, and determined they represent a key transitional form. The discovery helps explain how ambulacrarians diverged from chordates, the group including humans, over millions of years. Scientists previously thought the common ancestor of ambulacrarians resembled a worm, but Yujingia's anatomy suggests a tentacled ancestor more similar to modern starfish.
The team constructed a detailed family tree of 100 animal groups, both living and extinct, using 505 distinct characteristics, and placed Yujingia near the base of the ambulacrarian lineage. This fossil suggests that early ambulacrarians developed complex feeding structures before evolving hard skeletons or specialized body plans.
The researchers believe different ecological pressures drove the evolution of starfish and chordates along separate paths, starfish remained anchored and focused on particle feeding, while chordates developed movement and brains to actively seek food. Yujingia fills a crucial gap in understanding the early evolution of animal life.
