penultimate whorl in H. holmdelensis, a chamber arrangement typical of ancestral species of Hedbergella in the Cretaceous. In G. archeocompressa, the penultimate whorl is reduced to 5 chambers, which is typical of Globanomalina. The imperforate peripheral margin is a primary derived taxonomic character from H. holmdelensis and is present throughout the archeocompressa lineage. [Olsson et al. 1999]
Catalog entries: Globorotalia (Turborotalia) archeocompressa;Type images:
Short diagnosis: Test very small (<130 µm), flattened, with the spiral side nearly flat. Axial periphery rounded with slightly conical chambers. Final whorl with 5-6, chambers that increase very gradually in size. Umbilicus shallow and broad, open to the previous chambers. Aperture umbilical-extraumbilical, broad, low arch with narrow lip.NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.
Diagnostic characters: This is a very small-sized species, being less than 130 um in greatest diameter. It has a flattened compressed test with the spiral side being nearly plane. The axial periphery is rounded with slightly conical chambers which are nearly flat on the spiral side and project at a high angle towards the umbilicus. Five to six, compressed oval-shaped chambers that increase very gradually in size make up the ultimate whorl. The umbilicus is shallow and broad, open to the previous chambers, and contains sparse pustules on the umbilical shoulders of the surrounding chambers. The umbilical-extraumbilical aperture is a broad, low arch which is bordered throughout its extent by a narrow lip. The wall, which ranges from 4 to 7 um in thickness, is smooth and perforate. The pores which average 1 um at the narrowest point are mostly confined to the chamber surfaces away from the periphery which is largely imperforate. [Olsson et al. 1999]
|test outline:||Subcircular||chamber arrangement:||Trochospiral||edge view:||Concavo-convex||aperture:||Interiomarginal|
|umb chamber shape:||Inflated||coiling axis:||Low||periphery:||N/A||aperture border:||Thick flange|
|sp chbr shape:||Inflated||umbilicus:||Wide||periph margin shape:||Moderately rounded||accessory apertures:||None|
|umbilical or test sutures:||Moderately depressed||umb depth:||Shallow||wall texture:||Smooth||shell porosity:||Finely Perforate: 1-2.5µm|
|spiral sutures:||Moderately depressed||diameter mm:||0.139||width mm:||-||breadth mm:||-|
Geographic distribution: Western equatorial Pacific Ocean, coastal Gulf of Mexico, and South Atlantic Ocean (DSDP Site 356). [Olsson et al. 1999]
Aze et al. 2011 summary: Western equatorial pacific, Gulf of Mexico, south Atlantic Ocean; based on Olsson et al. (1999)
Isotope paleobiology: No data available. [Olsson et al. 1999]
Aze et al. 2011 ecogroup 3 - Open ocean thermocline. Based on light δ13C and relatively heavy δ18O. Sources cited by Aze et al. 2011 (appendix S3): this study
Phylogenetic relations: This species evolved from Hedbergella holmdelensis in late Biochron P0. [Olsson et al. 1999]
Most likely ancestor: Muricohedbergella holmdelensis - at confidence level 4 (out of 5). Data source: Olsson et al. 1999, fig 5a.
Notes: Upper Zone P0 to Zone Plb. Due to the very small size and rare occurrence of this species the upper range is not yet reliably established. [Olsson et al. 1999]
Last occurrence (top): at top of P1b subzone (100% up, 63.9Ma, in Danian stage). Data source: Olsson et al. 1999
First occurrence (base): in mid part of P0 zone (50% up, 66Ma, in Danian stage). Data source: Olsson et al. 1999
Plot of occurrence data:
Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 37
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, 1413 pp. Olsson, R.K.; Hemleben, C.; Berggren, W.A. & Huber, B.T., (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology. Smithsonian Institution Press, Washington, DC, 1-252 pp.
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, 1413 pp.
Olsson, R.K.; Hemleben, C.; Berggren, W.A. & Huber, B.T., (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology. Smithsonian Institution Press, Washington, DC, 1-252 pp.
Globanomalina archeocompressa compiled by the pforams@mikrotax project team viewed: 20-1-2018
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