Ophiuridae
A large family of brittle stars with simple, unbranched arms.
Ophiuridae is a large family of brittle stars within the suborder Ophiurina. Their arms are simple and lack branches, attaching firmly to the disc's edge and moving side to side. Short, movable spines on the arms lie flat when the animal is disturbed but stand upright when it is at rest. Both the disc and arms are covered with separate, visible scales, with these scales found on each side of the disc. A continuous ring of mouth papillae surrounds the jaw, and the base of each arm has either a single comb or both an inner and outer comb. Fossil evidence of this family goes back to the Carboniferous period, specifically the genus *Aganaster*†. The living genera include those sometimes placed in the family Ophioleucidae, which are here treated as the subfamily Ophioleucinae.
Quick Facts
- Taxon
- Ophiuridae
Facts from the source article.
Lore & Background
The family Ophiuridae is described as having arms that are simple and unbranched, projecting from and well-fused to the edge of the disc. These arms move horizontally. The arm spines are short and movable; they lie flat against the arms when stimulated but are held erect when the brittle star is at rest. The disc and arms are covered in naked, distinct scales, with scales situated at both sides of the disc. The jaw is surrounded by a continuous series of mouth papillae, and the base of the arm contains either a single arm comb or an inner and outer arm comb. Fossils of Ophiuridae date back to the Carboniferous period, represented by the extinct genus Aganaster†. The family includes several living genera, and some genera sometimes placed in the family Ophioleucidae are here included in Ophiuridae as the subfamily Ophioleucinae.
Reader's Guide
The significance of Ophiuridae lies in its status as a large family within the suborder Ophiurina, characterized by distinct morphological features such as simple unbranched arms, movable arm spines that respond to stimulation, and a continuous series of mouth papillae. The presence of naked, distinct scales on both disc and arms, along with the arm comb structure (single or inner and outer), provides key diagnostic traits. The fossil record extends to the Carboniferous, indicating an ancient lineage. The inclusion of genera sometimes placed in Ophioleucidae as a subfamily reflects taxonomic uncertainty that is preserved in the source. These features contribute to the family's role in understanding brittle star diversity and evolution, as documented in references such as the European register of marine species and the Handbook of the Marine Fauna of North-West Europe.
Did You Know?
- The arms of Ophiuridae are simple and unbranched, moving horizontally.
- Arm spines lie flat when stimulated but are held erect at rest.
- The family includes genera sometimes placed in Ophioleucidae as the subfamily Ophioleucinae.
Frequently Asked Questions
Who is Ophiuridae?
Ophiuridae is a large family of brittle stars nested within the suborder Ophiurina. Its members are defined by simple, unbranched arms that grip the disc's rim tightly and swing laterally rather than undulating vertically.
What are Ophiuridae's powers/role?
Each arm bears short, movable spines that flatten flush when the animal is disturbed yet snap upright during rest, giving it a built-in alarm response. The disc and arms are armored with separate, clearly visible scales on both sides, and a continuous ring of mouth papillae surrounds the jaw.
Why is Ophiuridae important?
As one of the larger families in Ophiurina, it showcases a wide range of body-plan variation, including differences in whether the arm base carries a single comb or a paired inner-and-outer comb. Its Carboniferous fossils also anchor the evolutionary timeline of ophiuroid brittle stars.
What's Ophiuridae's signature move?
The arms travel in a horizontal, side-to-side arc, producing a distinctive lateral swimming and crawling gait that sets the family apart from vertically undulating ophiuroids. Combined with the flat-when-startled, erect-at-rest spine behavior, this gives Ophiuridae a very recognizable motion profile.
More in Sea Cucumbers and Brittle Stars, Part 2 1-24
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