Catalog - Abathomphalus salajensis

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Other pages this level: A. asteroidalis, A. salajensis

Abathomphalus salajensis

Citation: Abathomphalus salajensis Solakius 1983

Type sample (& lithostrat): Holotype from sample KNA - 42 of section 4 (fig. 3) ; paratypes from sample E - 75 of section 2 (fig. 2) ;

Type age (chronostrat): lower part of the Rugotruncana gansseri Sub- zone of the sections.

Type locality: Kef en Nsoura, Enfidaville region, northeastern Tunisia

Type repository: Lund: Dept of Historical Geology and Palaeontology, University of Lund, Lund, Sweden.

Diagnosis: An Abathomphalus with small, concavo-convex, double keeled, slightly inflated and compressed test with subpetaloid chambers. Umbilicus shallow and covered by the tegilla; infralaminal accessory apertures and an interiomarginal extraumbilical primary aperture.

Description: Test small to medium sized, concavo-convex, compressed, subquadrate in outline, coiled in a low trochospire. Spiral side distinctly to slightly convex, umbilical side strongly to slightly concave, variable. Equatorial periphery subquadrate, slightly lobate, furnished with two well-developed, wide and irregularly spaced, thickened and faintly beaded keels. The second keel is placed on the umbilical side of the periphery, well visible in umbilical view. 9-14 chambers on the spiral side, arranged in 2-2½ whorls; 3-4 initial chambers, very small, increasing slightly in size. These are followed by 4, distinctly larger, gently inflated, sub- petaloid chambers which increase regularly in size. The last whorl constitutes most of the test and is composed of 3½-4, rarely 5, larger, slightly inflated chambers which are distinctly compressed just above the equatorial periphery, forming a peripheral ridge which represents the spiral part of the first keel. On the umbilical side the chambers are semi-circular to petaloid or crescentic in shape, gently inflated around the area of the keels, becoming more depressed towards the umbilicus. Sutures on the spiral side curved, distinctly to strongly beaded and depressed ; on the umbilical side radial, faintly beaded and depressed. Umbilicus quadrate, shallow, covered by the tegilla. The position of the primary aperture is interiomarginal extraumbilical. The 2-3 accessory apertures are infralaminal. Wall calcareous, perforate, except for the imperforate keels and tegilla. Surface spirally covered by small pustules. Pustule development variable between specimens.

Holotype: Max. diam. : 0.475 mm. Min. diam. : 0.40 mm. Thickness : 0.15 mm

In honor of Dr. Joseph Salaj, micropaleontologist at the Geological Institute of Dionyza Stura, Bratislava, in recognition of his work on the Foraminifera of Tunisia.

1969 - Abathomphalus intermedia (BOLLI) : Funnell, Friend & Ramsay, pp. 27, pl. 2, figs. 8-10, text-figs. 7- 9.

Main variation: Chambers arranged in 2-2½ whorls ; 3½-5 chambers in the last whorl. Umbilical side strongly or slightly concave.

Remarks: Abathomphalus salajensis nov. sp. is a definite Abathomphalus species as distinguished by the generic characters of concavo-convex, compressed test two wide irregularly spaced keels, the tegilla with infralaminal accessory apertures and the interiomarginal extranmbilical position of the primary aperture. The chambers are subpetaloid in shape and depressed.

The hypotype of Abathomphalus intermedia as described by B.M. Funnell et al. (1969) from Galicia bank, is synonymous with this species. I have examined this hypotype and found it to be identical to Abathomphalus salajensis nov. sp.
The new species Abathomphalus salajensis differs from its ancestor Globotruncanella havanensis (VOORWIJK) in having a concavo-convex, compressed test with less inflated chambers, wider tegillar area and a true double keel. The transitional forms between these two species have a more inflated concavo-convex test than Abathomphalus salajensis nov. sp., more lobate chambers in the last whorl (similar to those of Globotruncanella havanensis) but more compressed umbilically and furnished with a weakly developed double keel. The tegilla is well-developed showing clearly the appearance of infralaminal accessory apertures. The primary aperture is interiomarginal extraumbilical. These similarities between Globotruncanella havanensis and transitional forms are sufficient evidence to show the evolution of Abathomphalus salajensis nov. sp. from Globotruncanella havanensis. The double keel of Abathomphalus salajensis nov. sp. has evolved from the imperforate band of Globotruncanella havanensis through the strenghtening of the marginal parts of the band. The 3½-4, lobate to subglobular chambers of the last whorl of Globotruncanella havanensis have become more depressed through its evolution to Abathomphalus salajensis nov. sp. The smaller tegllla of the former species and its accessory apertures becomes broader and well-developed in the latter.

Abathomphalus salajensis nov. sp. differs from its descendant Abathomphalus intermedius in having smaller test, less inflated and more compressed chambers, fewer chambers in the last whorl and less developed pustules on both sides of the test. The keels of one variety of Abathomphalus intermedius (variety II, see description of A. intermedius), are wider and more irregularly spaced than those of Abathomphalus salajensis nov. sp. and in another variety of Abathomphalus intermedius (variety I, see description of A. intermedius), the second keel appears indistinctly or distinctly on the final whorl, while the keels of Abathomphalus salajensis nov. sp. are more weakly beaded and more widely spaced.

Occurrence: Abathomphalus salajensis nov. sp. was first described as Abathomphalus intermedia (BOLLI) by B.M. Funnell, J.K. Friend & A.T.S. Ramsay (1969) from the Upper Maastrichtian of the Galicia bank, west of Spain, which according to these authors represents the Abathomphalus mayaroensis Zone. The same species, on the other hand, first appears in the Tunisian sections of Kef en Nsoura, in the base of the Rugotruncana gansseri Subzone and ranges to the lowermost part of the Abathomphalus mayaroensis Subzone.

Stratigraphical range: From the base Rugotruncana gansseri Subzone to the lowermost part of the Abathomphalus mayaroensis Subzone, Upper Maastrichtian.

Depository : Holotype and paratypes of Abathomphalus salajensis nov. sp. are deposited in the type collection of the Department of Historical Geology and Palaeontology, University of Lund, Lund, Sweden.

References:

Solakius, N. (1983c). Solakius, N. (1983). Morphological and phylogenetic studies of the species of the genus Abathomphalus Bolli, Loeblich &. Geobios. 16: 139-159. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Abathomphalus salajensis Solakius 1983

Abathomphalus salajensis

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