Oegophiurida

Oegophiurida is an order of brittle stars, class Ophiuroidea.

The physical characteristics of this order include well separated lateral plates, which exposes the oral surface of radial ossicles. It also has vertebrae with streptospondylous (hourglass) articulation, which thus allow for vertical and horizontal movements.^[1] The order has neither oral nor radial shields. They have paired serial gonads arranged segmentally along the arm. The hyponeural groove is covered by soft integument, which forms a spacious epineural canal that is not closed over by ventral arm plates. The disk is covered by naked or granulated skin, or by imbricating scales.^[2]

Oegophiurida is extinct, except for a recent species, Ophiocanops fugiens, which has several remarkable features. In each arm there is a single digestive caecum. The caecum wall has many folds which enlarge the absorbing surface. This is similar to the structure in asteroids. Nothing however, is known of this species' microscopic structure of its gut.^[3] Its gonads also stretch into the arms, also common to asteroids. Both of these are hardly present in other orders of the class. The skeleton is similar to other ophiuroids, except the paired right and left vertebrae are not fused, albeit set in orderly fashion. Also absent is ventral arm plates and radial and oral shields. Previously, Oegophiurida was known only to exist from the lower Ordovician to the upper Carboniferous periods. However most features of O. fugiens conform to this order, such as the absence of genital plates and genital bursae. They also lack dorsal or ventral arm plates.^[2] However, some recent studies have challenged the classification of O. fugiens as Oegophiurid.^[4]

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