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Lophocyrtis pegetrum (Sanfilippo and Riedel, 1970)

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Cyclampterium? pegetrum Sanfilippo and Riedel 1970 n. s p .
Plate 2. figures 8 - 10


Description: Shell robust, campanulate to subcylindrical. with the abdomen usually constituting a half or more of the volume of the shell. Cephalis subspherical, poreless
or with rather few small pores, in many specimens bearing a short, often thick, apical spine. Collar stricture pronounced. Thorax hemispherical, thick-walled, with sub-regular circular pores, and a surface which is smooth, thorny or nodose. Abdomen usually subcylindrical
or slightly expanding distally. rarely invertedhemispherical, with irregular robust meshwork much coarser than that of the thorax, in some specimens closed distally. Some specimens have three, or rarely more, irregular, subcylindrical feet which may be terminal or subterminal. and which arise, not at the lumbar stricture, but more distally.


Measurements: Based on 30 specimens from cores CHUB 17; MP 5-1 ; JOIDES 3. 358 ' ; JYN V 16P; SDSE 90. 104 - 105 cm. Total length 310 - 620 Ám. usually 340-470 Ám . Length of thorax 75-155 Ám , its maximum breadth 124-210 Ám.


Remarks: This species is distinguished from Cyclampterium ? leptetrum by the coarser meshes of the abdominal wall and generally smaller dimensions of the thorax, and from some Eocene forms, such as Podocyrtis triacantha Ehrenberg and Alacorys tetracantha (Ehrenberg), by the more irregular abdominal wall (and feet, when present) and generally more robust thoracic wall. As it is defined here. Cyclampterium ? pegetrum includes a wide variety of forms, and later investigation may permit its subdivision into two or more species.
Particularly significant in this connection may be an increase in the size of the thorax with time. It is about 85 Ám long and 140 Ám wide in specimens from MP 5-1, and about 150 Ám long and 200 Ám wide in specimens from SDSE 90. 104-105 cm. Other possible bases for species
distinctions may be the presence or absence of feet, and whether they are terminal or subterminal, and the presence or absence of nodular thickenings on the thoracic wall.


The specific name is derived from the Greek pegos=strong, and etron=abdomen.


Some early representatives of Cyclampterium ? have the abdomen (with meshes smaller than in early specimens of C. ?pegetrum) drawn out distally as three latticed feet. We have found only a f ew such specimens, and illustrate one as Cyclampterium ? sp. (plate 2, figure 7).
Sanfilippo and Riedel 1970
Lophocyrtis ( Cyclampterium ) pegetrum (Plate II, 3-5 )


Remarks: Lophocyrtis ( Cyclampterium ) pegetrum is distinguished from its ancestor L. (C.) milowi by the median thoracic length being greater than 90 ttm and, when feet are present, by these being solid rather than latticed. From its descendant L. (C.) leptetrum it differs by its shorter (90-125/~m vs. 150-165 ~m) thorax and coarser abdominal meshes. L. (C.) pegetrum differs from mid latitude morphotypes of L. (Paralampterium) dumitricai by its larger thorax and from L. (P.) ? galenum by having a longer abdomen without a differentiated termination and by not having the feet ridged and pored.

New observations (on 30 specimens from DSDP Site 73 Cores 13, 14; Site 77B Core 34; Site 289 Cores 64, 69, 71, 75; Site 315A Core 9; Site 366 Core 5 and Site 515B Cores 25, 30, 36): total length 215-620 Ám; length of thorax 75-155 Ám, width 125-215 Ám, number of pores around the circumference 20-30; length of abdomen 85-340 Ám, width 160-300 Ám, number of pores around the circumference 6-15. No horn; some specimens have a thickened cap over the cephalis.
L. (C.) pegetrum is rare to moderately abundant from its evolutionary transition from L. (C.) milowi in the early Dorcadospyris ateuchus Zone to the middle of the Cyrtocapsella tetrapera Zone, where it evolves into L. ( C. ) leptetrum (latest Oligocene to Early Miocene).
Sanfilippo 1990


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