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Calocycletta (Calocycletta) cladara Sanfilippo and Riedel, 1992

Description - Add description

Three-segmented pterocorythid with the cephalis distinctly pored, bearing a rather strong, slightly bladed horn. Generally, the lateral lobes of the cephalis are indistinct, and do not cause a distinct break in its contour. Thorax inflated-conical to subspherical, with pores irregular in size and arrangement, which in late forms tend to be larger near the collar stricture and with their bars joining the cephalis above the level of the collar pores (pl. 2, figs. 14, 15). The thoracic wall is a thin, porous lamella proximally. becoming much thicker distally where the pore frames are high. Abdomen distinctly more delicate than the thorax, irregularly ubcylindrical, often constricted medially; when observed complete, which is rarely, terminated with a thin poreless peristome bearing small teeth. In late forms the row of pores just below the lumbar stricture increase in size to two or three times the size of the surrounding pores (pl. 2, fig. 14).

Distinguishing characteristics:
This species differs most markedly from others of the genus by the lack of regular pore arrangement. It bears a superficial resemblance to some species of Albalrossidium and Lamprocyclas, but tracing its evolution revealed its true relationship to Calocycletta virginis. In the latest members of the latter species, the thoracic porcs lose their strict regular arrangement, the horn tends to become bladed. and some specimens have a delicate abdomen lacking teeth. It differs from Pterocorys minythorax (Nigrini) by its larger thorax (P. minythorax thoracic width 63-72pm; length of cephalothorax 63-81pm), its irregular pore arrangement and the tendency in later forms to develop larger pores at the collar and lumbar strictures. The theoperid Stichocorys johnsoni Caulet is confusingly similar. It also displays the larger pores just below the lumbar stricture and the same sinous abdomen, but it has a simple cephalis.
C. cladara left no descendants, and thus terminates the subgenus Calocycletta (Calocycletta).

Type material: Holotype (pl. 2, fig. 13) from DSDP Site 83A, Core 15

Stratigophy: Late Miocene/Early Pliocene; Stichocorys peregrina Zone.

(based on a total of 50 specimens from DSDP Site 77B, Cores 13-14; Site 83. Core 15; Site 216. Core 1; Site 217, Core 4; Site 310. Core 9); Length (excluding horn) 110-215 μm (usually about 165 μm), length of cephalothorax 75-110 μm; width of thorax 80- 105 μm, width of abdomen 85-135μm (usually about 110μm).

The name is the neuter form of the Greek adjective kladaron, wavy, an allusion to the profile of the abdomen.

The transition from C. virginis to C. cladara occurs near the boundary between the Dorcadospyris alata Zone and the Diartus petterssoni Zone (Middle Miocene), and C. cladara becomes extinct in the lower part of the Stichocorys peregrina Zone (near the Miocene/Pliocene boundary). C. cladara occurs in low abundance in all of the Miocene assemblages of the appropriate age from latitudes lower than 40°. It reaches its highest abundances (up to 5% of the total assemblage) in the Late Miocene Indian Ocean assemblages.

Sanfilippo and Riedel 1992











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