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Description

"Cyathoceras irregularis Cairns, 1982

 

Description. Corallum ceratoid, straight to irregularly bent, attached by thin, encrusting, slightly expanded base. Pedicel one fourth to one third of GCD. Holotype 13.7 x 10.5 mm in CD and 14.9 mm tall; largest specimen 15.4 x 14.6 mm in CD and 18.4 mm tall. Theca smooth and procelaneous, covered by very small, low granules. Costae occurring near calicular edge and base, if at all. Calice round to elliptical. Septa hexamerally arranged in four or five cycles; however, fifth cycle never complete: largest specimen with 72 septa. Up to 48 septa stage Si and S2 equal in size, moderately exsert, and extending to columella. S3 and S4 progressively narrower and less exsert. With addition of S5, septal arrangement becomes irregular.

 

May have one or two pairs of S5 in each system. If only one pair present, enclosed (flanked) S4 invariably larger than unflanked S4. If both pairs of S5 present, both S4 enlarged, reaching almost as far toward columella as S3. Occurrence of all degrees of S5 development in one corallum possible, i.e., systems with 0, 1, or 2 pairs of S5, making interpretation of septal cycles con fusing. Inner edges of S1-3 broadly sinuous, corresponding to transverse septal undulations, but inner edges of higher-cycle septa straight. Large, blunt granules present on septal faces, usually arranged in lines along crests of septal undulations. Columella large, composed of numerous slender, twisted ribbons usually fused into solid mass.

 

Remarks. All specimens examined were attached to dead coral, usually Solenosmilia variabilis. The type-locality is a seamount or ridge, which supports a presumed deepwater coral bank composed primarily of S. variabilis. C. irregularis is similar to Cyathoceras squiresi Cairns, 1979, in its association with the framework coral of deepwater banks. C. squiresi is often attached to Enallopsammia profunda, a common constituent of western Atlantic deepwater banks.

 

Discussion. For the purposes of this comparison the following ten species are considered valid Cyathoceras: C. cornu Moseley, 1881; C. rubescens Moseley, 1881; C. tydemani Alcock, 1902; C. diomedeae Vaughan, 1907; C. niinoi Yabe and Eguchi, 1942; C. foxi Durham and Barnard, 1952; C. woodsi Wells, 1964; C. squiresi Cairns, 1979; C. avis (Durham and Barnard, 1952); and C. hoodensis (Durham and Barnard, 1952). C. quaylei Durham, 1947, is herein transferred to Labyrinthocyathus, on the basis of an examination of the paratypes (USNM 547417), which have columellas composed of inter connected lamellae. C. irregularis can be distinguished from all of these species by its fused columella, composed of closely united, poorly defined, twisted ribbons; other Cyathoceras have well-defined columellar elements. It is also distinguished by the irregularity of development of the fifth-cycle septa.

 

Etymology. The specific name irregularis refers to the irregular manner in which the S5 are added.

 

Material. Types.Types. The holotype, collected at Eltanin station 1346, is deposited at the United States National Museum (47165). Seven paratypes, also collected at Eltanin station 1346, are deposited at the United States National Museum (47166), and one paratype from this station is deposited at the British Museum.. (1979.11.3.1). Type-locality: 54°49'S, 129°48'W (seamount or ridge on Heezen fracture zone of Eltanin fracture zone system); 549 m.

 

Distribution. Known only from type-locality (Map 4)." Cairns 1982, Plate 6, figs. 6-9.

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© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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