Echinothurioida
The Echinothurioida are an order of sea urchins belonging to the class Echinoidea. They are characterized by their distinctive, often colorful and spiny tests (skeletons), and include some of the largest and most visually striking sea urchin species. These urchins are found in a variety of marine habitats, from shallow coral reefs to the deep sea.
Common Names
Echinothurioida are commonly referred to as "pencil urchins" or "slate pencil urchins" due to the elongated, often cylindrical shape of their spines.
Characteristics
Echinothurioida possess several defining characteristics:
- Test (Skeleton): Typically large and often flattened or slightly dome-shaped.
- Spines: Long, slender, and often cylindrical or needle-like. They can be very brittle and easily broken. In some species, the spines can be brightly colored.
- Pedicellariae: Small, pincer-like structures that help the sea urchin defend itself and clean its test.
- Tube Feet: Short and numerous, used for locomotion and feeding.
- Aristotle's Lantern: A complex jaw apparatus used for grazing on algae and other food sources.
Environments
Echinothurioida are found in a variety of marine environments, including:
- Coral Reefs: Some species are found in shallow water, inhabiting coral reefs and rocky substrates.
- Deep Sea: Other species are found in deeper waters, dwelling on the seafloor.
- Tropical and Subtropical Regions: Echinothurioida are primarily found in tropical and subtropical regions.
References
For further information on Echinothurioida, consult these resources: