Major Subgroups in Phylum Echinodermata

Introduction

Echinodermata is a phylum of marine animals found throughout the ocean. This phylum is the largest without any freshwater or terrestrial forms. Dating back to the lower Cambrian it is comprised of around 7000 living, or extant, species and 13000 extinct species.

The phylum is comprised of seven classes, six of which survive to the present day.

* Asteroidea
* Blastoidea (extinct)
* Concentricycloidea
* Crinoidea
* Echinoidea
* Holothuroidea
* Ophiuroidea

Asteroidea reproduced with permission from Wikipedia	Concentricycloidea reproduced with permission from Palaeos.com	Crinoidea reproduced with permission from Wikipedia
Echinoidea reproduced with permission from Wikipedia	Holothuroidea reproduced with permission from Wikipedia	Ophiuroidea reproduced with permission from Wikipedia
	Blastoidea reproduced with permission from Wikipedia

All of the six classes that made it made it through to the modern era have distinguishing features:

• Asteroidea (asteroids / starfish or sea stars): 1,500 species that capture prey for their own food.
• Concentricycloidea (sea daisies), have a unique water vascular system.
• Crinoidea (crinoids / feather stars or sea lilies): 600 species that are suspension feeders.
• Echinoidea (echinoids / sea urchins and sand dollars): 1,000 species; members of that class have movable spines.
• Holothuroidea (sea cucumbers): 1,000 species, elongated animals resembling slugs.
• Ophuiroidea (brittle stars and basket stars), the largest class of echinoderms.

Fossil forms included Blastoids, Edrioasteroids and several peculiar Early Cambrian animals such as Helicoplacus, Carpoids, Homalozoa and possibly Machaerids.

go on to next chapter to find out more about the subclasses in subphylum Asterozoa

or go back to the title page...

• Characters/ anatomy
• Fossil record
• Modern forms
• Glossary
• Literature and web links
• Back to main page

Author: Elizabeth Sweet
Last updated: 22nd November 2005
Return to Fossil groups home page