They belong to the Echinoidea, one of the five classes of the phylum Echinodermata, the others being holothurians, crinoids, starfish and brittlestars. Like all echinoderms, echinoids have a skeleton ...

Invertebrate Paleontology; Carbonate Sedimentology; Paleozoic Coal Swamps; Measuring Mg/Ca ratios of permineralized plants and marine invertebrates (echinoderm crinoids) found in Late Pennsylvanian ...

It was not so terribly long ago; that the original planktonic mix gave birth to some zillion critters with the advantage of ...

They belong to the Echinoidea, one of the five classes of the phylum Echinodermata, the others being holothurians, crinoids, starfish and brittlestars. Like all echinoderms, echinoids have a skeleton ...