Cyathidium meteorensis spec. nov., ein neuer Crinoie aus der Familie Holopodidae

Abstract

Cyathidium meteorensis spec. nov., a new crinoid of the family Holopodidae. The new species, dredged on the eastward slope of the Great Meteor Bank, must be referred to the genus Cyathidium ST~NSTI~UP, 1847, which seemed to have become extinct at the end of

Microscopical Anatomy of the Cyrtocrinid Cyathidium meteorensis (sive foresti) (Echinodermata, Crinoidea)

“…The present study on Cyathidium meteorensis extends the morphological data given in the primary description (Fechter 1973) with data on ossicle surface, on stereom structure, and on histology and internal characteristics of viscera. The structural features are compared with those of Holopus and another cyrtocrinid species, Gymnocrinus richer; (Heinzeller et al, in press).…”

“…The histological data of the gut of Cyathidium, both openings of which were already recognized by Cherbonnier andGuille ( 1972) andFechter ( 1973), show it to be simply endocyclic, describing all together one coil without accessory glands or remarkable diverticles. As far as can be decided from the merely light microscopical view, its cellular composition resembles that of other crinoids (LaHaye and Holland, 1984;Heinzeller and Welsch, 1994).…”

“…Like other members of the family Holopodidae, Cyathidium meteorensis does not develop syzygial or synarthrial articulations (Fechter 1973) but only muscular/ligamentary ones. These, however, display two quite unusual details.…”

Development of Cyathidium foresti (Echinodermata: Crinoidea, Cyrtocrinida) from early attached larvae to adult-like juveniles

“…The genus Cyuthidium is represented by two recent species, C. foresti (Cherbonnier and Guille 1972; identical with C. meteorensis, Fechter 1973) and C. plunfei (Heinzeller et al 1996). Cyathidium protects the delicate distal parts of the arms and the vulnerable oral surface of the body under a hard shelter formed by proximal arm pieces, namely by an outer circle of wide and trapezoidal axial primibrachials and an inner circle of five pairs of conically shaped first secundibrachials.…”

“…All these 15 ossicles of the shelter fit closely together. The unusual existence of a single primibrachial per ray has been thought to result from the fusion of what were originally two primibrachials (Bather 1900;Briinnich Nielsen 1913) but 'there is no proof that this is so' as Rasmussen pointed out in 1961. Fechter (1973 was the first to recognize that juveniles actually have two primibrachials.…”