CATALOG OF ORIGINAL DESCRIPTIONS: Laeviheterohelix Nederbragt, 1991

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> L -> Laeviheterohelix
Other pages this level: Laeviheterohelix, Lazarusina, Leupoldina, Lilliputianella, Lilliputianelloides, Lipsonia, Liuella, Liuenella, Loeblichella, Lunatriella,

Daughter taxa: (blue => in age window 0-800Ma)
= Laeviheterohelix flabelliformis
= Laeviheterohelix turgida

Laeviheterohelix

Citation: Laeviheterohelix Nederbragt, 1991
Rank: Genus
Type species: Guembelina pulchra Brotzen 1936

Current identification/main database link: Laeviheterohelix Nederbragt, 1991


Original Description
Diagnosis: Test calcareous, biserial throughout or with an initial planispiral coil; wall microperforate and smooth with scattered pustules, or with pores situated in the center of a pore mound. Aperture a simple arc, bordered by distinct flanges.

Etymology: the Latin word "laevis" means smooth

Extra details from original publication
Remarks: The genus Laeviheterohelix is here proposed for the smooth heterohelicids (L. pulchra. L. glabrans, L. dentata, and two new species, L. turgida and L. flabelliformis). The wall structure of these forms differs from that of other heterohelicids, in being non-costate and microperforate; the average pore-size is around 0.8µm. All other heterohelicid species are costate and have larger pores. Heterohelix moremani is the single other species that may have a smooth test; but such smooth forms occur together with costate specimens.

Two types of wall structure are found in Laeviheterohelix specimens. The wall is either smooth with scattered pustules in between which the pores are situated or the wall is covered with small mounds in the center of which the pores are found. The same two types of wall structure occur in two other planktic foraminiferal genera, in Cassigerinella Pokomy (Saito and Biscaye 1977) and in Guembelitria Cushman (Kroon and Nederbragt 1990). The wall structure of Laeviheteroltelix differs qualitatively from that of the other costate heterohelicids. Alignment of pustules on microperforate specimens from less well preserved scdiments can give the appearance of costae, but such structures appear to be diagenetic rather than primary. Laeviheterohelix pulchra is the only species known to have a smooth morphotype as well as one covered with pore mounds. Apart from wall structure the two types are morphologically identical. However, all specimens in a single population from one location have the same wall structure. The difference may be ecophenotypic.

Range: Turonian to end of the Maastrichtian.

References:

Kroon, D. & Nederbragt, A. J. (1990). Ecology and paleoecology of triserial planktic foraminifera. Marine Micropaleontology. 16: 25-38. gs

Nederbragt, A. J. (1991). Late Cretaceous biostratigraphy and development of Heterohelicidae (planktic foraminifera). Micropaleontology. 37: 329-372. gs

Saito, T. & Biscaye, P. E. (1977). Emendation of Riveroinella martinezpicoi Bermúdez and Seiglie, 1967, and synonymy of Riveroinella with Cassigerinella Pokorný, 1955. Micropaleontology. 23: 319-329. gs


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Laeviheterohelix compiled by the pforams@mikrotax project team viewed: 15-11-2019

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