Phrynophiurida
An order of brittle stars including basket stars, with leathery skin.
Phrynophiurida, once known as Euryalae, is an order of brittle stars that includes basket stars. Their leathery skin is covered with calcareous granules or small plates. They have bursae for gas exchange and waste removal. The ventral arm shields are underdeveloped, and dorsal shields are usually missing. Some arms are branched and can coil vertically. The vertebrae connect via hourglass-shaped joints. The madreporite sits on the oral surface. Digestive glands stay within the central disc. These animals mostly live in deep-sea waters, where they coil their arms around branched black coral.
Within the order, Asteronychidae have a large disk and slender arms, while Asteroschematidae have a small disk and stout arms. The family Ophiomyxidae stands apart with its soft, unprotected skin, similar to that of Ophiocanops, but lacks the unique gut and gonad features of oegophiurids. Phrynophiurida is split into two suborders: Euryalina (with families Asteronychidae, Asteroschematidae, Gorgonocephalidae, and Euryalidae) and Ophiomyxina (with family Ophiomyxidae). Some modern studies support including Ophiocanopidae, but this is not yet widely accepted.
Quick Facts
- Taxon
- Phrynophiurida
Facts from the source article.
Lore & Background
Phrynophiurida have bursae for gas exchange and excretion. Their ventral arm shields are rudimentary, and dorsal shields are usually absent. The arms are sometimes branched and can coil vertically. The vertebrae are joined by hourglass-shaped surfaces. The madreporite is on the oral surface. Digestive glands are confined to the central disc. The integument is leathery, bearing calcareous granules or platelets. They generally live in deep-sea waters, coiling their arms on branched black coral.
Reader's Guide
The Phrynophiurida are significant as an order of brittle stars that includes the distinctive basket stars. Their leathery integument with calcareous granules or platelets sets them apart from other brittle stars. The order is divided into suborders Euryalina and Ophiomyxina. Within Euryalina, families include Asteronychidae (large disk, slender arms), Asteroschematidae (small disk, stout arms), Gorgonocephalidae, and Euryalidae. The Ophiomyxina family Ophiomyxidae has a soft, unprotected integument like that of Ophiocanops, but lacks the peculiar gut and gonad features of oegophiurids. The inclusion of Ophiocanopidae is supported by some modern studies but not yet generally accepted. Their deep-sea habitat and coiling behavior on black coral are notable ecological traits.
Did You Know?
- Phrynophiurida were formerly called Euryalae.
- Their arms can be branched and can coil vertically.
- The madreporite is located on the oral surface.
Frequently Asked Questions
What is Phrynophiurida?
Phrynophiurida is an order of brittle stars that includes the well-known basket stars. It was formerly grouped under the name Euryalae before being reclassified into its current taxonomic position.
How do Phrynophiurida handle breathing and waste removal?
These brittle stars use specialized structures called bursae, which simultaneously manage gas exchange and the expulsion of metabolic waste from the body.
What is unusual about the arm skeleton in this order?
The vertebrae link together via hourglass-shaped joint surfaces, and the ventral arm shields are only rudimentary while dorsal shields are typically absent entirely.
Where do Phrynophiurida live and how do they anchor themselves?
They are predominantly deep-sea dwellers that grip the branching structure of black coral by coiling their arms vertically around the branches.
How does the skin of Phrynophiurida differ from other brittle stars?
Their skin has a leathery feel and is studded with tiny calcareous granules or small plates, giving it a subtly armored texture unlike the smoother skin of many related orders.
More in Sea Cucumbers and Brittle Stars 1-24
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