Catalog - Helvetiellinae

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Helvetiellinae

Citation: Helvetiellinae Longoria & Gamper 1984

Type species: Helvetiella Longoria and Gamper 1984

Tests trochospirally coiled, chambers inflated spherical, ovoid, hemispherical to angulo-truncated. Last whorl of chambers often displaying shift in axis of coiling. Primary aperture interio-marginal, umbilical in position, apertura! apparatus consisting of spirai system of tegilla. Periphery rounded without indication of keel to truncated with dorsal rim or well-developed single keel. Surface hispid, spinosopapillate ornamentation, consisting of massive papillae becoming axially elongated to form spines arranged in parallel rows latitudinally oriented, giving tests a roughened appearance

Remarks: The Helvetiellinae differ from the Globotruncaninae in having hispid, papillate tests instead of smooth to slightly pustulose surface ornamentation. They differ from the Rugoglobigerininae in lacking meridionally oriented costellae or rugosities (pl. 2). The origin of helvetiellids is still uncertain. The helvetiellids may have originated from a rugoglobigerinid ancestor via the development of massive papillae, perhaps as an ecologic adaptation (text-fig. 2).

Helvetiellids are considered as a specialized stock of planktonic foraminifera. lt is possible that they represent a migration of warm-water species to cool-water realms in Maastrichtian time (this conclusion is supported by their abundance in higher latitude faunas). Consequently, helvetiellids may represent an important component of the high latitude faunas that can be used as paleobiogeographic indicators connecting both low and higher latitude faunal realms.

The helvetiellids may be significant in understanding the migration of Tethyan faunas to the northern and southern latitudes. At the same time, their migration pattern would be indicative of paleo-oceanographic currents such as those that Berggren (1962) proposed to explain the invasion of Tethyan faunas in higher latitudes during Maastrichtian time.

Finally, helvetiellids may prove to be useful for correlating Maastrichtian strata of different paleogeographic provinces.

Range: Maastrichtian.

Occurrence: World·wide.

References:

Longoria, J. F. & Gamper, M. A. (1984). Subfamily Helvetiellinae, a new group of Late Cretaceous (Maastrichtian) planktonic foraminifera. Micropaleontology. 30: 171-179. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Helvetiellinae Longoria & Gamper 1984

Helvetiellinae

References:

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