When were echinoderms discovered, and how?

They were discovered the first time a human saw a starfish, probably washed up on a beach or clinging to rocks in a tidepool. read more

Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes (a superphylum), after the chordates (which include the vertebrates, such as birds, fishes, mammals, and reptiles). read more

The oldest known echinoderm may be the Vendian fossil Arkarua, found in southern Australia. It was soft-bodied but may have had some sort of unmineralized plates on its body. The Vendian fossil Tribrachidium may have been related to the echinoderms, but this is still debated. read more