Science
Fact-checked

At AllTheScience, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.

Learn more...

What are Echinoderms?

Echinoderms, from starfish to sea urchins, are a fascinating group of marine animals known for their radial symmetry and spiny skin. They play a crucial role in ocean ecosystems and have unique features like regenerative abilities. Their world is as mysterious as it is vital. How do these creatures thrive beneath the waves? Join us to uncover their secrets.
Michael Anissimov
Michael Anissimov
Michael Anissimov
Michael Anissimov

Echinoderms are a very old phylum of marine animals whose name means "spiny skin" in Greek. This name is a misnomer, however, because not all echinoderms have spines. Their more fitting universal trait is common ancestry, including a unique water-based vascular system, and frequent five-fold symmetry. Though they do not always display five-fold symmetry (sea cucumbers are echinoderms, and they have bilateral symmetry), echinoderms are known for often playing games with the typical bilateral symmetry trend, as in sea urchins (radial symmetry), and the numerous starfish and sand dollars (five-fold symmetry). Echinoderms are one of several phyla that is exclusively marine.

The first known echinoderm is thought to be Arkarua, an ancient disc-like fossil about 1 cm in diameter with a five-fold pattern of dents that leads scientists to classify it as a likely echinoderm. This fossil dates to the Late Ediacaran, about 550 million years ago. Other than that, the first certain echinoderms appear in the Early Cambrian, about 530 million years ago. Containing 7,000 living species, echinoderms are the second-largest phylum of deuterostomes after the chordates (vertebrates), which are the dominant large-bodied phylum on land.

Starfish are echinoderms.
Starfish are echinoderms.

Very flexible, echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone, miles upon miles beneath the surface. There are two primary subphyla of echinoderms; the motile Eleutherozoa, which includes starfish, brittle stars, sea urchins, sand dollars, sea daisies, and sea cucumbers; and the sessile Pelmatozoa, which includes the crinoids (feather stars). The mobile subphyla crawls along the ocean floor using a muscular foot, and is specialized to consume bottom-dwellers that few other ocean animals can.

Sea cucumbers are a type of echinoderm.
Sea cucumbers are a type of echinoderm.

Echinoderms are significant because they are among the only large animals capable of surviving in the utter desert that characterizes the vast majority of the world's oceans. Their skeletons readily fossilize and provide important biogeographical information to paleontologists. Many limestone formations are made out of echinoderm skeletons, and some paleontologists believe that the evolutionary radiation of echinoderms was responsible for a sudden increase in the diversity of marine Mesozoic life.

Michael Anissimov
Michael Anissimov

Michael is a longtime AllTheScience contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...
Michael Anissimov
Michael Anissimov

Michael is a longtime AllTheScience contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...

You might also Like

Discuss this Article

Post your comments
Login:
Forgot password?
Register:
    • Starfish are echinoderms.
      By: Giuseppe Porzani
      Starfish are echinoderms.
    • Sea cucumbers are a type of echinoderm.
      By: Andrea Izzotti
      Sea cucumbers are a type of echinoderm.