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Aphetocyrtis catalexis Sanfilippo and Caulet, 1998

Description - Add description

Description: The apical spine is included in the cephalic wall, protruding distally as a small apical horn, usually as long as the length of the cephalis, and bearing discrete dimples at its base. Paired mitral arches on the inner wall of the cephalis give it a flattened appearance, and the horizontal secondary lateral spines are clearly visible dorsally. Cephalis small, poreless, or with very small, subcircular pores. The wall of the cephalis is thick, giving it the appearance of being sunken into the wall of the proximal part of the thorax. Thorax inflated conical, with quincuncially arranged pores. Lumbar stricture marked by an internal ring, moderately to well expressed externally. The thoracic pores continue across the lumbar stricture. Abdomen varies from subcylindrical to inverted conical. Upper part of abdomen is as broad as the maximum width of the thorax. Abdomen distally wavy in early forms. becoming inverted conical towards the end of the Late Oligocene. The abdominal pores are larger than the thoracic ones (up to twice) in some early forms. but they are usually smaller in the last representatives of the species. Termination ragged.

Etymology: The name is derived from the Greek noun katalexis (feminine) meaning end or termination.

Distinguishing characteristics: A. catalexis is distinguished from A. rossi by commonly having an apical horn with small dimples at its base and a shorter inverted conical abdomen. It is less variable than the other species in this lineage.

Distribution: Endemic to Antarctic. First occurrence in the Lychnocanoma conica Zone (27 to 28 Ma): last occurrence in the L. conica Zone (20 to 24 Ma).
Sanfilippo and Caulet 1998











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