Catalog entries: Calocyclas costata
Original description: Cephalis ovate, lobed, with sparse subcircular to circular pores and bearing a stout, conical apical horn. Thorax subspherical, with pores circular, hexagonally arranged and with a pronounced tendency to longitudinal alignment, the longitudinal rows separated by pronounced costae. No lumbar stricture externally. Abdomen subcylindrical or tapering distally, narrower than the widest part of the thorax. Abdominal pores subcircular or circular, arranged hexagonally with apparent longitudinal alignment (these longitudinal lines are continuous with those of the thorax) and often with longitudinal ridges separating pore rows. Terminal feet eleven to eighteen in number, lamellar, usually truncate, parallel or slightly convergent, broader than the spaces between them, usually situated opposite alternate rows of abdominal pores.
Based on 30 specimens. Length of apical horn 115-230 µ; of cephalis 30-45 µ; of thorax 70-100 µ; of abdomen 10-33 µ; of feet 12-70 µ. Breadth of cephalis 38-53 µ; of thorax 103-135 µ; of abdomen (distally) 75-108 µ. Distinguishing characters (rw): This species is distinguished from Calocyclas virginis by the pronouncedly costate thorax and otherwise smooth shell surface.
This species is distinguished from all others of the genus by the longitudinal ribs between the rows of thoracic pores, and the consequently very smooth contour. In addition to this, it differs from co-occurring specimens of C. virginis in that the latter usually have a distinct change in contour where the horn leaves the cephalis, and a more abrupt collar stricture. It differs from C. caepa Moore (1972; a member of the C. robusta group of Riedel and Sanfilippo, 1978a, p.66) in that the latter has a bladed horn, and a more delicate abdomen with smaller, more numerous pores, terminating in short, triangular teeth. There is a superficial resemblance also to Calocyclas turris Ehrenberg (1873), but that is an Eocene species with the simple cephalis characteristic of the theoperids. (Sanfilippo et al., 1985)
Remarks on original description: Although rare specimens appear to be transitional between Calocyclas virginis and Calocyclas costata, it is now considered advisable to recognize the two as distinct species. Transitional forms are to be expected if Calocyclas costata arose from Calocyclas virginis, as appears to have been the case.
Last occurrence (top): within Neogene Period (2.59-23.03Ma, top in Piacenzian stage). Data source: Lazarus et al. 2015 - "N age group"
First occurrence (base): within Neogene Period (2.59-23.03Ma, base in Aquitanian stage). Data source: Lazarus et al. 2015 - "N age group"
Plot of occurrence data:
Riedel, W. R. & Sanfilippo, A. (1970). Radiolaria, Leg. 4 DSDP. Initial Reports of the Deep Sea Drilling Project. 4: 503-575. gs Riedel, W. R. & Sanfilippo, A. (1978a). Stratigraphy and evolution of tropical Cenozoic radiolarians. Micropaleontology. 23(1): 61-96. gs Riedel, W. R. (1959). Oligocene and Lower Miocene Radiolaria in tropical Pacific sediments. Micropaleontology. 5(3): 285-302. gs
Riedel, W. R. & Sanfilippo, A. (1970). Radiolaria, Leg. 4 DSDP. Initial Reports of the Deep Sea Drilling Project. 4: 503-575. gs
Riedel, W. R. & Sanfilippo, A. (1978a). Stratigraphy and evolution of tropical Cenozoic radiolarians. Micropaleontology. 23(1): 61-96. gs
Riedel, W. R. (1959). Oligocene and Lower Miocene Radiolaria in tropical Pacific sediments. Micropaleontology. 5(3): 285-302. gs
Calocycletta costata compiled by the radiolaria@mikrotax project team viewed: 21-10-2020
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