Sand dollars, when alive aren’t white and smooth, they’re actually purple and spiny. Living along the seafloor, their skeleton is a remarkable feat of engineering.
Ever wondered what a sand dollar looked like while it was alive? Those little skeletons we collect from the beach actually used to be covered in purple spines and tube feet, and collected in groups along the ocean floor, looking nothing so much as dozens of purple sea cookies.
“Pristine white sand dollars have long been the souvenir to commemorate a successful day at the beach. But most people who pick them up don’t realize that they’ve collected the skeleton of an animal, washed up at the end of a long life. As it turns out, scientists say there’s a lot to be said about a sand dollar’s life. That skeleton — also known as a test — is really a tool, a remarkable feat of engineering that allows sand dollars to thrive on the shifting bottom of the sandy seafloor, an environment that most other sea creatures find inhospitable.”