Oegophiurida
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Zeugophiurina |
Oegophiurida is an order of 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. Nothing however, is known of this species' microscopic structure of its gut.[3] 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].
[edit] Notes
- ^ Meglitsch, Paul A (January 1, 1991). Invertebrate Zoology. Oxford University Press US, 562. ISBN 0-19-504900-4.
- ^ a b Fell, H.B. (1963). The Phylogeny of Sea-Stars. Philosophical Transactions of the Royal Society of London, 406-7.
- ^ M.Jangoux, J.M. Lawrence (editors) (June 1, 1982). Echinoderm Nutrition. CRC Press, 278. ISBN 90-6191-080-3.
- ^ Pawson,D.L.,Phylum Echinodermata, Zootaxa 1668: 749–764 (2007)
