Unexpected Tentacles: Yujingia glutenotunica

Publication Info:

Transcript:

Kaiyue He et al. 2026. Cambrian fossils illuminate the ambulacrarian common ancestor. Current Biology 36 (20): 5180-5190; doi: 10.1016/j.cub.2026.08.053

Meet Yujingia glutenotunica, the earliest starfish relative ever discovered. At 518 million years old, it had some unexpected features.

Episode 363

Notes:

What do you think the earliest starfish looked like? Do you think they look kind of like worms or do you think they look more like tunicates or anyway, we might finally now have an answer. Starfish or sea star evolution has been tricky actually the the evolution of all echinoderms. So, starfish, urchins, crinoids, you name it. And they all belong to the group Ambulacraria which also includes hemichordates like acorn worms. And that's where it gets really kind of tricky because Ambulacraria is an old group and I do mean old. It is pretty much the other branch of deuterostomes. When the origin of a group is that old, there aren't necessarily going to be any great or obvious fossils. And they couldn't even be too sure about what body plan they were looking for because acorn worms have bilateral symmetry like us. Well, starfish have a five-fold radial symmetry which just is weird. Well, this half a billion-year-old fossil is finally giving us some clues. Meet Yujingia glutenotunica. And when I say half a billion years old, I'm not exaggerating. It is 518 million years old. Yujingia had a soft tube or bottle-shaped body and then tentacles at one end for gathering food. It also had appendages at the other end most likely for anchoring itself. Which means that while paleontologists were looking for something a little more worm-like or at least more like an acorn worm, the ancestor of the whole group was a lot more like a starfish or a crinoid. As usual, if you want more information, here's the source.