pforams@mikrotax - Planoglobanomalina

Citation: Planoglobanomalina Olsson&Hemleben, 2006

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]

Distinguishing features:
Parent taxon (Globanomalinidae): Hedbergellids - trochospiral, mostly low trochospiral. Apertures of earlier formed chambers remain visible around the umbilicus.
This taxon: Planispiral, compressed, loosely coiled, numerous chambers in final whorl, last 1-3 chambers uncoiling.
Aperture equatorial, oval-shaped with broad lip.

Description

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]

Smooth, normal perforate. [Olsson & Hemleben 2006]

Biogeography and Palaeobiology

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): at top of E7b subzone (100% up, 45.7Ma, in Lutetian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within E6 zone (50.20-50.67Ma, base in Ypresian stage). Data source: Total of ranges of species in this database

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). E. J. Brill, Leiden. 2: 1-1413. gs

Olsson, R. K. & Hemleben, C. (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Globanomalina, Planoglobanomalina n. gen and Pseudohastigerina. In, Pearson, P. N., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 41(Chap 14): 413-432. gs O

Pearson, P. N. et al. (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. gs

Planoglobanomalina

Taxonomy

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

References:

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Comments

Daughter taxa (time control age-window is: 0-800Ma)
			Planoglobanomalina pseudoalgeriana Test loosely coiled, evolute, and compressed; 9-10 chambers in the final whorl, last three chambers showing a trend towards uncoiling.
			Planoglobanomalina sp. Specimens which cannot be assigned to established species