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Cycladophora rosetta Lombari and Lazarus, 1988

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Description: Cephalis is simple, of medium size, hemispherical. While most specimens have numerous irregularly shaped pores on the cephalis, some specimens exhibit a hyaline cephalis. There are two apical horns approximately the same length as the diameter of the cephalis. Cephalis is depressed into the upper thorax creating a fairly well developed spinal furrow. Lateral spines arc not expressed externally. Upper thorax is compressed, moderately flared and flat in outline with irregularly shaped pores. These pores are subdivided by an interior lattice creating four to six small petal-shaped or subcircular pores within the larger pore. Pores are arranged in staggered horizontal rows. Pore bars are narrow and of moderate thickness. The shell has a general spongy appearance due to the interior lattice-work of the pores. There is no obvious pore size gradient. Upper thoracic suture is smoothly shouldered. Lower thorax is equant to elongate, moderately to strongly flared, and centrally inflated. Pores in all but the last 1-2 rows are as those of the upper thorax, irregular in shape, filled with lattice, and arranged in staggered horizontal rows. The last rows of pores are open, variable in shape and medium to large in size. There is a gradual, weak pore size gradient increasing distally. The pore bars are narrow and of moderate thickness, free of ornamentation. Lower thoracic suture is sharply constricted. Abdomen or terminal segment consists of 1-2 horizontal rows of open, small to medium, irregularly shaped pores. Pore bars are moderately wide and fairly thick, free of ornamentation. There is usually a peristome present with one row of short teeth. The basal opening is closed by a plate which has numerous irregularly shaped, small pores.
Type: DSDP Site 173, core 28, section 2, 44 cm. England finder number E29/3.
Origin of name: From the Latin rosette, small rose. Name refers to the divided pores of the upper and lower thorax.
Comments: Cycladophora rosetta is distinguished by the complex lattice-work in the pores of the upper and lower thorax. This unique feature was not seen in any other cycladophorid except C. campanula. This latter species differs from C. rosetta in possessing a larger cephalis and lower thorax (text-fig. 10), a well-developed upper thorax, a more rounded lower thorax outline, and in the style of the interior lattice-work in the pores, it being less regularly arranged in C. campanula.
Occurrence: Cycladophora rosetta is restricted to the North Pacific, and has been recorded in our DSDP Site 173 samples from 173-29-2,41 cm through 173-28-1,145 cm. This species is generally few-to-common in abundance.
Lombari & Lazarus 1988











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