Around 500 million years ago, a strange ancestor of the modern sea star, sea urchin, and sand dollar swam above the Paleozoic seafloor. Classified as a pleurocystitid, the animal resembled an armored stingray in its appearance, armed with what looked like a set of swooping antennae.
But the insights that these robots provide about animal movement aren’t restricted to modern animals. According to Desatnik and colleagues, these robots also mimic the motion of ancient creatures, such as pleurocystitids. The robots revealed that the side-to-side swish of the animal’s stem would’ve propelled the pleurocystitid forward. They also revealed that a longer stem would’ve propelled the pleurocystitid forward faster than a shorter stem, a fact that’s seemingly supported in Paleozoic fossils, which featured longer and longer tails over time.