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Lophocyrtis brachythorax
(Sanfilippo and Riedel, 1970)
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Description - Add description
Cyclampterium ? brachythorax Sanfilippo and Riedel. n. sp.
Plate 2. figures 15-16
Description: Shell moderately robust, approximately oblate-ellipsoidal in over-all form. Cephalis subspherical, poreless or with a few small pores. The thorax is broadly conical proximally, then expands rapidly and contracts distally, so that it is 1.5-2 times as broad as it
is long. Thoracic pores are circular, regular, increasing in size distally from the slight collar stricture. Thoracic surface thorny. Abdomen rarely preserved, closed, ranging from a slightly convex cap to hemispherical, with pores similar in size to those of the thorax but less regular.
Measurements: Based on 16 specimens from cores AMPH 6P, 18-20 cm, and 52-54 cm.; PROA 96P, 439-441 cm. and 538-540 cm.; SDSE 87, 499-500 cm. and 799-800 cm. Total length 220-310 µm. Length of thorax 125-195 µm, its maximum breadth 240-335 µm.
Remarks: This species is distinguished from C. ? tanythorax and C. ? neatum by the pronounced compression of the thorax along the axis of the shell.
The specific name is derived from the Greek brachys=short, and thorax. | | Sanfilippo and Riedel 1970 | Lophocyrtis (Cyclampterium)brachythorax (Plate IV, 4-6)
Remarks: Lophocyrtis ( Cyclampterium ) brachythorax is distinguished from L. (C.) neatum (its descendant) and from L. (C.) tanythorax (its ancestor) by its greatly compressed thorax. The transition into and out of L. (C.) brachythorax is rapid and transitional morphotypes are very rare.
The original description has been augmented with new measurements based on 20 specimens from DSDP Site 77B Cores 17-20 and Site 289 Cores 26-40. An apical horn is
not present. Total length 220-310 µm; of thorax 125-195 µm; of abdomen 0-145 µm. Maximum width of thorax 240-335 µm; of abdomen 120-250 µm. Number of pores around
the maximum circumference of the thorax 44-54. The abdomen (preserved in only a few specimens) is rarely oriented as to enable pores to be counted.
L. (C.) brachythorax occurs rarely in the middle Miocene, from its evolutionary origin at the boundary between the Dorcadospyris alata and Diartus petterssoni Zones to its evolutionary transition to L. (C.) neatum in the middle of the Didymocyrtis antepenultima Zone. | | Sanfilippo 1990 |
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