Starfish are officially grouped within the class Asteroidea (sea stars) within the phylum Echinodermata (echinoderms). This phylum includes other invertebrates that also have radial symmetry and calcium carbonate skeletons, such as sea cucumbers, brittle stars, sea urchins and crinoids (sea lilies). read more
They are invertebrates but evolutionarily they are the closest invertebrate plum to the vertebrates. They are the one invertebrate phylum that develops the mouth as the second opening during development and the anus as the first - like vertebrates they are deuterostomes. read more
No. A starfish has a hard shell and its inside is only organs. To be considered a vertebrate the starfish would need a spine and an internal skeleton (not to mention a head). They are, therefore, classified as invertebrates. read more
My students need 35 starfish dissection kits in order to examine an invertebrate. Is it a vertebrate or an invertebrate is a concept that becomes more relevant to a student if they can actually see the animal in order to justify an answer. read more