Planoglobanomalina


Classification: pf_cenozoic -> Globanomalidae -> Planoglobanomalina
Sister taxa: Globanomalina, Muricohedbergella, Planoglobanomalina, Pseudohastigerina, Turborotalia,
Daughter taxa: (blue => in age window 0-300Ma)
Test loosely coiled, evolute, and compressed; 9-10 chambers in the final whorl, last three chambers showing a trend towards uncoiling.
Specimens which cannot be assigned to established species

Taxonomy

Citation: Planoglobanomalina Olsson and Hemleben, 2006
Rank: Genus
Type species: Planoglobanomalina pseudoalgeriana Olsson & Hemleben 2006
Taxonomic discussion: Based on his study of the early Eocene KANE 9 core in the eastern equatorial Atlantic Ocean, Blow (1979) proposed that Pseudohastigerina danvillensis (Howe and Wallace) had an independent line of descent from other members of the genus, which he proposed was from Globorotalia (Turborotalia) planoconica Subbotina (= Globanomalina planoconica in this work), in contradiction to the views of Cordey and others (1969) who had considered P. danvillensis as a junior synonym of P. micra. He concurred with their view that P. micra had evolved from Pseudohastigerina wilcoxensis (Cushman) and that P. wilcoxensis, in turn, had evolved from Globanomalina at the base of Zone P6. Specialists have ignored Blow’s suggestion that there were two independent origins for the genus Pseudohastigerina. However, our examination of assemblages from ODP Hole 865B from the equatorial Pacific and recent drill-cores from Tanzania (Pearson and others, 2004) confirm Blow’s earlier observations of a separate origin for a planispiral morphotype in the early Eocene that is morphological similar to Pseudohastigerina. This necessitates the naming of a new genus, because unlike Blow (1979) we do not permit polyphyletic form -genera in our classification.
Blow derived Pseudohastigerina danvillensis from Globorotalia (Turborotalia) planoconica ( =Globanomalina planoconica) and illustrated specimens of G. planoconica from Zone E8 (see discussion below on the taxonomy of planoconica) that showed apertures that extended slightly onto the spiral side as well as specimens of P. danvillensis showing equatorial apertures. His observations do indeed illustrate a linkage between these Eocene morphotypes of G. planoconica and the derivation of a planispiral morphology. He was, however, incorrect in his identification of Pseudohastigerina danvillensis, which is a junior synonym of Pseudohastigerina micra (see discussion below). We have also observed a similar transitional morphology in ODP Hole 865B and Tanzania Drilling Project Site 2, but starting in Zone E6. The planispiral morphotype is more openly coiled and planispirally evolute with a tendency towards uncoiling of the last few chambers in the ultimate whorl (Plate 14.2, Figs. 5, 8-10). The test is much compressed and the chambers in axial view have a pinched periphery and show an ogyval shape that Blow emphasized as a distinguishing characteristic in separating his P. danvillensis ( =P. micra) from P. micra. Morphotypes with 9 to 10 elongated chambers in the ultimate whorl are closely homeomorphic with the Aptian planispiral species Globigerinelloides algerianus (Plate 14.2, Fig. 5). These morphotypes do not appear to range above Zone E8. Other characteristics of all these morphotypes include recurved sutures and somewhat broad apertural lips that fuse with previous lips to form an apertural rim around the umbilicus. In some specimens, as was noted
by Blow, relict apertures open where the lips are not completely fused.
The planispiral to almost planispiral morphotypes derived from Globanomalina planoconica are herein placed in the new genus Planoglobanomalina and the type species for the new genus is the new species Planoglobanomalina pseudoalgeriana.
[Olsson & Hemleben 2006]

Catalog entries: Planoglobanomalina;

Type images:

Distinguishing features: Planispiral, compressed, loosely coiled, numerous chambers in final whorl, last 1-3 chambers uncoiling.
Aperture equatorial, oval-shaped with broad lip.

NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
They are being edited as the site is developed and comments on them are especially welcome.

Description


Diagnostic characters: Planoglobanomalina n. gen. is distinguished from the homeomorphic genus Pseudohastigerina by its more compressed test, pinched periphery and ogyval-shaped chambers in edge view. Planoglobanomalina is more loosely coiled, more evolute, and the last few chambers show a tendency towards uncoiling. Pseudohastigerina is more tightly coiled, more involute, and develops bipartite, biumbilicate apertures in some specimens, in contrast to Planoglobanomalina, which has a single primary aperture and in some specimens relict apertures between fused apertural lips.
[Olsson & Hemleben 2006]

Wall type: Smooth, normal perforate. [Olsson & Hemleben 2006]

Test morphology: Test asymmetrical to fully
planispiral, compressed, loosely coiled, evolute to partially involute, oval in outline, chambers compressed, elongate, numerous chambers in ultimate whorl, last one to three chambers in ultimate whorl arranged in an uncoiling trend, apertural lips of chambers in the ultimate whorl fuse to form a somewhat broad shelf that extends around the umbilicus, relict apertures present where apertural lips are not completely fused; primary aperture equatorial, asymmetric to symmetric, an oval shaped opening bordered by a broad lip, test much compressed with a pinched periphery which gives the chambers an ogyval shape.
Size: Maximum diameter of type species 0.39 mm, thickness 0.12 mm.
ETYMOLOGY.— Named after Globanomalina, the ancestor of this genus and in recognition of its planispiral coiling.
[Olsson & Hemleben 2006]

Biogeography and Palaeobiology


Phylogenetic relations: Planoglobanomalina n. gen. evolved from Globanomalina planoconica and left no descendants.
[Olsson & Hemleben 2006]

Most likely ancestor: Globanomalina - at confidence level 0 (out of 5). Data source: .

Biostratigraphic distribution

Geological Range:
Notes: Zone E6 to Zone E8.
[Olsson & Hemleben 2006]
Last occurrence (top): in lower part of Lutetian Stage (24% up, 46.2Ma, in Lutetian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Ypresian Stage (66% up, 50.6Ma, in Ypresian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Primary source for this page: Olsson & Hemleben 2006 - Eocene Atlas, chap. 14, p. 418

References:

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea), 2. E. J. Brill, Leiden, 1413 pp.

Olsson, R.K. & Hemleben, C., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Globanomalina, Planoglobanomalina n. gen and Pseudohastigerina. In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera. Cushman Foundation Special Publication. 41 Allen Press, Lawrence, Kansas, pp. 413-432.

Pearson, P.N. & others, (2004). Paleogene and Cretaceous sediment cores from the Kilwa and Lindi areas of coastal Tanzania: Tanzania Drilling Project Sites 1–5. Journal of African Earth Sciences, 39: 25-62.


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Planoglobanomalina compiled by the pforams@mikrotax project team viewed: 15-12-2018

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