CATALOG OF ORIGINAL DESCRIPTIONS: Globotruncana fornicata ackermanni Gandolfi 1955
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Citation: Globotruncana fornicata ackermanni Gandolfi 1955taxonomic rank: sub-speciesType specimens: PL 2, fig. 5a-c, 6a-c, 7a-c ; 20836: type description p.42Type sample (& lithostrat): Km. 92 section, S. 5608Type age (chronostrat): Campanian-MaastrichtianType locality: A section near Km. 92 on the Fonseca-Riohacha road, Rancheria Valley, 40 km. north of Fonseca, NE part of the State of Magdalena, northern Colombia.Type repository: Ithaca, New York; Paleontological Research Institution
Original Description Similar to the previous one with more outstanding convexity on the dorsal side, chambers short, strongly inflated especially on the ventral side, the last one occasionally more elongated and arched with well-developed median inner depression. Sutures on the ventral side radial, depressed, being somewhat raised only around the umbilical margin. Only the last chamber may still show a more or less continuous raised suture. The test is rougher than in Glt. fornicata fornicata and Glt. fornicata plummerae with spinose tubercles on the surface of the early chambers. Frequent tests are sinistrally coiled. Size: Dimensions of holotype: Width 0.36 x 0.30 mm.; thickness, 0.29 mm Etymology: named after E. D. Ackerman, Exploration Manager of International Petroleum (Colombia), Limited. Extra details from original publication Remarks.— Morphologically this form is similar to Glt. marginata austinensis; however, the elongated, arched chambers (especially the last ones), the median inner marginal depression, the dorsal convexity are distinctive for the species.
Rare tests appear in the uppermost PuUenia cretacea zone and Siphogenerinoides bramlettei zone (PI. 2, fig. 6a-c, 7a-c) with chambers and keels oblique to the plane of coiling but diverging along the direction of coiling. In one specimen a dichotomic keel was observed.
Rosalinella globigerinoides Marie (see p. 33) shows a similar oblique arrangement of chambers and keels but differs in the less elongated last chambers which are symmetrically inflated on both sides and less increasing in size. An oblique arrangement ot the chambers, diverging keels are shown also by Glt. mayaroensis, and Glt. intermedia intermedia. A dichotomic keel was up to the present known only to Glt. imbricata Mornod, 1948, ( Turonian).
References:
Gandolfi, R. (1955). The genus Globotruncana in northeastern Colombia. Bulletins of American Paleontology. 36: 1-118. gs
Globotruncana fornicata ackermanni compiled by the pforams@mikrotax project teamviewed: 11-9-2024
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holotype illus-462.jpg
holotype illus-462.jpg
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