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Eurystomoskevos petrushevskaae Caulet, 1991

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Eurystomoskevos petrushevskaae
Shell two-segmented, thick-walled. Cephalis conical with small circular pores. Apical horn robust of variable length, but always longer than the cephalis. Vertical spine small, never protruding outward. Collar stricture indistinct. Upper thorax cylindrical, with small secondary thorns and three transverse rows of subcircular pores. Primary lateral and dorsal spines extend through the walls of the upper thorax, and protrude outward as external wings. Lower thorax flared with progressively large sub-polygonal pores. No termination.
Remarks. A new genus is created for this species because no similar morphologic characters exist in previously erected genera. Petrushevskaya (1975) has figured, and briefly described, this form as a member of the genus Diplocyclas. However, the type species of Diplocyclas (D. bicorona Haeckel, 1887, p. 1392, pi. 59, fig. 8) has a well-organized peristome and a strong vertical spine protruding as a long cephalic horn. The type species of Coniforma (C. antiochensis Pessagno, 1969, p. 397, figs. 9-12) has a shell with a similar external outline, but with a complex cephalic structure including massive internal elements.
Dimensions. (Measured on holotype, paratypes and specimens of the same age). Length of cephalic horn: 35-70 µm; of cephalis: 20-25 µm; of thorax: 75-90 µm. Maximum breadth of thorax: 75-110 µm.
Caulet 1991











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