Globigerinella megaperta


Classification: pf_cenozoic -> Globigerinidae -> Globigerinella -> Globigerinella megaperta
Sister taxa: G. adamsi, G. calida, G. radians, G. siphonifera, G. clavaticamerata, G. molinae, G. navazuelensis, G. obesa, G. praesiphonifera, G. pseudobesa, G. roeglina, G. megaperta, G. wagneri, G. sp.,

Taxonomy

Citation: Globigerinella megaperta Rögl, 1994
Rank: species
Synonyms:
Taxonomic discussion:

Globigerinella megaperta and closely related G. wagneri are unique to the Paratethys and possess a globigerinid wall of high pore porosity and wall structure of coalescing ridges with evidence of spine collars, as is diagnostic of the bulloides-type wall. Based on these features, together with the extraumbilical-to equatorial position of the aperture, they are placed in Globigerinella, although it is important to point out that they do not have the typical bulloides-type wall of pore diameters less than 1µm. Some specimens may display a sac-like last chamber and/or aberrant chambers. This also co-occurs in G. wagneri (Rögl, 1994). [Spezzaferri et al. 2018]

Catalog entries: Globigerinella megaperta

Type images:

Distinguishing features: Aperture unusually open and highly arched, formed from final 4 chambers; initial coiling streptospiral,

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:

This species is characterized by the unusually open and highly arched interiormarginal aperture and streptospiral initial coiling mode, producing a form reminiscent of Globigerinella siphonifera, to which it is not closely related. It differs from G. wagneri by the more developed and more open high arched aperture and tendency towards planispiral coiling. Globigerinella megaperta can be distinguished from G. obesa and G. praesiphonifera by the gaping aperture that reveals the final four chambers compared to the latter species in which the apertural opening is restricted to the last chamber. It differs from these species by its greater pore density and pore size. [Spezzaferri et al. 2018]


Wall type: Spinose; spines are supported by spine collars, which coalesce to form ridges. Pore concentrations range from around 85-90 pores/50 μm2 test surface area and pore diameters range from around 2-3.5 μm.

Test morphology: low trochospiral to pseudoplanispiral, inner coil depressed, lobulate in outline with depressed and straight sutures on both sides. Eleven chambers are arranged in 2½ whorls, the chambers of the inner whorls are very small, the 5-6 globular chambers of the last whorl increase rapidly in size, the last 4 chambers open into the large and deep umbilicus. The aperture is a very large and high asymmetrical arch interiomarginal becoming marginal, and bordered by a thick rim. [Spezzaferri et al. 2018]

Size: Diameter of the holotype from 0.45 mm. [Spezzaferri et al. 2018]

Character matrix

test outline:Lobatechamber arrangement:Pseudoplanispiraledge view:Equally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Globularcoiling axis:Very lowperiphery:N/Aaperture border:N/A
umb chbr shape:Globularumbilicus:Wideperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Strongly depressedumb depth:Deepwall texture:Cancellateshell porosity:Macroperforate: >2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:5.0-6.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: This species has been found only in Haute Savoie and Central Paratethys. [Spezzaferri et al. 2018]

Isotope paleobiology: No data available. [Spezzaferri et al. 2018]

Phylogenetic relations: Globigerinella megaperta evolved from G. wagneri in lower Oligocene Zone O3 and can be considered as an end member of a unique Paratethys globigerinellid lineage. [Spezzaferri et al. 2018]

Most likely ancestor: Globigerinella wagneri - at confidence level 3 (out of 5). Data source: Spezzaferri et al. 2018.

Biostratigraphic distribution

Geological Range:
Notes: This species was described from the late Rupelian and Chattian of the Austrian Molasse Basin (Rögl, 1994; Cicha and others, 1998) corresponding to the interval spanning Zone O4 to O5. The specimens documented by Ujetz and Wernli (1994) from Zone P20 in Haute Savoie (French Alps) allow the extension of its range down to Zone O3. [Spezzaferri et al. 2018]
Last occurrence (top): within O5 zone (26.93-28.09Ma, top in Chattian stage). Data source: Spezzaferri et al. 2018
First occurrence (base): within O3 zone (29.18-30.28Ma, base in Rupelian stage). Data source: Spezzaferri et al. 2018

Plot of occurrence data:

Primary source for this page: Spezzaferri et al. 2018 - Olig Atlas chap.6 p.192

References:

Cicha, I., Rögl, F., Rupp, C. & Ctyroká, J. (1998). Oligocene-Miocene foraminifera of the central Paratethys. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft. 549: 1-325. gs

Rögl, F. (1994). Globigerina ciperoensis (Foraminiferida) in the Oligocene and Miocene of the central Paratethys. Annalen des Naturhistorischen Museums in Wien. 96A: 133-159. gs

Spezzaferri, S., Coxall, H. K., Olsson, R. K. & Hemleben, C. (2018a). Taxonomy, biostratigraphy, and phylogeny of Oligocene Globigerina, Globigerinella, and Quiltyella n. gen. In, Wade, B. S. , Olsson, R. K. , Pearson, P. N. , Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication. 46(Chap 6): 179-214. gs

Szekely, S. -F. & Filipescu, S. (2016). Biostratigraphy and paleoenvironments of the Late Oligocene in the north-western Transylvanian Basin revealed by the foraminifera assemblages. Palaeogeography, Palaeoclimatology, Palaeoecology. 449: 484-509. gs

Ujetz, B. & Wernli, R. (1994). “Globigerina ciperoensis”, atypically giant planktonic foraminifers from the Oligocene of the Haute-Savoie, France. Annalen des Naturhistorischen Museums in Wien. 96A: , , 199-207. gs


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Globigerinella megaperta compiled by the pforams@mikrotax project team viewed: 18-10-2019

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