Ophiuridae are a large family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of brittle star

Brittle star

Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...

s of the suborder 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...

.

Description

The arms are simple and unbranched, projecting from and well-fused to the edge of the disc. These arms move horizontally. The arm spines short and movable. They lie flat against the arms when stimulated, but held erect when the brittle star is at rest. Disc and arms are covered in naked, distinct scales. The scales are situated at both sides of the disc.

The jaw is surrounded by a continuous series of mouth papillae. The base of the arm contains a a single arm comb or an inner and outer arm comb.

Systematics and phylogeny

The fossils of Ophiuridae date back to Carboniferous

Carboniferous

The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 (Aganaster†). The family includes the following living genera:

• Anthophiura
• Astrophiura
• Dictenophiura
• Euvondrea
• Gymnophiura
• Haplophiura
• Homophiura
• Ophiambix
• Ophioceramis
• Ophiochalcis
• Ophiochorus
• Ophiochrysis
• Ophiocrates
• Ophiocrossota
• Ophioctenella
• Ophiocypris
• Ophioelegans
• Ophiogona
• Ophiolipus
• Ophiomisidium
• Ophiopenia
• Ophiophyllum
• Ophiopleura
• Ophiopyren
• Ophiopyrgus
• Ophiosphalma
• Ophiosteira
• Ophioteichus
• Ophiotjalfa
• Ophiotylos
• Ophiotypa
• Ophiozona
• Ophiura
• Ophiuraster
• Ophiurinae
• Ophiuroglypha
• Sinophiura
• Spinophiura
• Stegophiura
• Theodoria
• Uriopha

(This list includes the genera sometimes placed in the family Ophioleucidae, here included in Ophiuridae as the subfamily Ophioleucinae).