Not to be confused with Ophiuroidea, the class that contains Ophiurida.

The Ophiurida are an order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of echinoderm

Echinoderm

Echinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....

s within the class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Ophiuroidea. It includes the vast majority of living brittle stars.

Characteristics

The upper surface of the disk of Ophiurida is covered with scales.
They have bursa

Bursa (anatomy)

A bursa is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of slimy fluid . It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce friction between the bones and allows free movement...

e for respiration and excretion, dorsal and ventral arm shields are present and usually well developed. Arms are unbranched and incapable of coiling vertically. Most are five-armed, some with 4 or 6 arms as an abnormality, but others properly bear six or seven arms. The madreporite

Madreporite

The madreporite is a lightcolored calcerous opening used to filter water into the water vascular system of echinoderms. It acts like a pressure-equalizing valve. It is visible as a small red or yellow button-like structure, looking like a small wart, on the aboral surface of the central disk of a...

 is on the oral surface. The digestive glands are entirely within the central disc. They move their arms side to side by means of ball-and-socket joints. Tropical species tend to contrast color from the environment, but most others prefer to blend in. These biochromes do not include echinochromes. Some species exhibit luminescence

Bioluminescence

Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

, but only for short periods when stimulated, generally on the bases of the arm spines.

Systematics and phylogeny

There is currently no consensus as to the subdivision of the Ophiurida.
The order has been divided into the following suborders and infraorders

• Ophiomyxina
• Ophiurina
  Ophiurina
  Ophiurina are a suborder of brittle stars containing the majority of living brittle star species.-Systematics:There is currently no consensus as to the subdivision of the Ophiurina . It contains the genera Amphiura, Amphipholis, and Ophiacantha.The suborder has been divided into the following...
  
  
  • Hemieuryalina
  • Chilophiurina
  • Gnathophiurina
    Gnathophiurina
    The Gnathophiurina are a group of Ophiuroidea mostly treated as suborder .-Families:* Amphilepididae Matsumoto, 1915...
    
    
  • Ophiodermatina
  • Ophiolepidina

Another classification scheme divides it into the following suborders:

• Chilophiurina Matsumoto, 1915
• Laemophiurina Matsumoto, 1915
• Ophiothricidae
  Ophiothricidae
  Ophiothricidae are a family of ophiurid brittle stars within the infraorder Gnathophiurina.All have arms with delicate translucent, thorny spines. The arms are flexible in all directions. The jaws contain clusters of well-developed tooth papillae on the apex but not on the sides. There are no...
  
   Ljungman, 1867 (= Ophiotrichidae)
• Ophiurina
  Ophiurina
  Ophiurina are a suborder of brittle stars containing the majority of living brittle star species.-Systematics:There is currently no consensus as to the subdivision of the Ophiurina . It contains the genera Amphiura, Amphipholis, and Ophiacantha.The suborder has been divided into the following...
  
   Müller & Troschel, 1840

Another classification scheme divides it as:

• Chilophiurina
• Laemophiurina
• Gnathophiurina
  Gnathophiurina
  The Gnathophiurina are a group of Ophiuroidea mostly treated as suborder .-Families:* Amphilepididae Matsumoto, 1915...
  
  

Ecology

Ophiurida have a world-wide distribution range and are found in oceans in different depths. Most of them are herbivore

Herbivore

Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s or detritus

Detritus

Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...

feeders.