Globigerinoides eoconglobatus


Classification: pf_cenozoic -> Globigerinidae -> Globigerinoides -> Globigerinoides eoconglobatus
Sister taxa: G. elongatus, G. extremus, G. conglobatus, G. eoconglobatus, G. obliquus, G. altiaperturus, G. joli, G. neoparawoodi, G. kennetti, G. bollii, G. italicus, G. ruber, G. mitra, G. seigliei, G. subquadratus, G. diminutus, G. bulloideus, G. sp.,

Taxonomy

Citation: Globigerinoides eoconglobatus Stainbank, Spezzaferri, Kroon, de Leau & Rüggeberg, 2018
Rank: Species
Basionym: Globigerinoides eoconglobatus Stainbank, Spezzaferri, Kroon, de Leau & Rüggeberg, 2018
Taxonomic discussion:

Distinguishing features: It is distinguished from G. obliquus by its last chamber, which is less laterally compressed. It also has numerous supplementary apertures. It differs from G. conglobatus primarily by its wide, high aperture and inflated final chamber in adult specimens. An additional distinguishing feature is the coiling, which is tight and streptospiral in G. conglobatus and loosely coiled in G. eoconglobatus n. sp.

Discussion: To identify G. conglobatus we have strictly followed the ‘‘morphospecies’’ concept used in Wade et al. (2017, in press). We have defined it by a series of morphological characters that are shared with the holotype. Consequently, G. eoconglobatus n. sp., having different characters has been identified as a new morphospecies. Therefore, both G. conglobatus and G. eoconglobatus n. sp. may or may not represent true biological species. Forms similar to G. eoconglobatus n. sp. have been identified as G. conglobatus or its synonyms by several authors (e.g., Bé and Tolderlund 1971; Fordham 1979; Rillo 2016; Rillo et al. 2016). Yet, due to the lack of accompanying figures in the majority of publications, it is difficult to ascertain the true extent of this morphospecies distribution. Currently, based on this study and images from Rillo (2016) we can state it is found in the Indian and Pacific Oceans.

Catalog entries: Globigerinoides eoconglobatus

Type images:

Distinguishing features: Like G. obliquus, but final chamber less laterally compressed.

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


Wall type: Normal perforate, cancellate, spinose, ruber/sacculifer-type wall texture and conglobatus-type wall texture of Hemleben et al. (2018). The primary wall texture of G. eoconglobatus n. sp. is ruber/sacculifer type. However, similarly to G. conglobatus, individuals were found with calcitic crusts with a conglobatus-type wall texture (Hemleben et al. 2017, in press) (Fig. 2, 5–6). This texture represents a modification of the external ruber/ sacculifer-type wall texture: the high density of thin spines supported by short spine collars are partly covered by calcite crusts during gametogenesis. The result is a hummocky texture of overgrown spine collars, which occasionally show spine holes that may further develop in a thick euhedral calcite crust (Hemleben et al. 2018).

Test morphology: Low to moderately high trochospiral consisting of two whorls, quadrangular to circular in outline and markedly lobate. Chambers are subspherical, four in the last whorl gradually increasing in size. The last chamber is slightly laterally compressed. Sutures depressed and straight on both sides. Umbilicus open and deep. Primary aperture umbilical to slightly extraumbilical, medium-sized to high and a wide arch. Several small to moderately high and rounded sutural supplementary apertures on the spiral side. It has a high density of thin spines

Size: generally >250 µm. Maximum diameter of the holotype is 548 µm.

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical
sp chamber shape:Globularcoiling axis:Low-moderateperiphery:N/Aaperture border:N/A
umb chbr shape:Globularumbilicus:Wideperiph margin shape:Broadly roundedaccessory apertures:Sutural
spiral sutures:Strongly depressedumb depth:Deepwall texture:Cancellateshell porosity:Macroperforate: >2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:4.0-4.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Currently, based on this study and images from Rillo (2016) we can state it is found in the Indian and Pacific Oceans.

Phylogenetic relations:

Aze et al. (2011) reported the evolution of G. conglobatus from G. obliquus in the Late Miocene. As such, it is inferred that G. eoconglobatus n. sp. evolved from G. obliquus in Subzone M13a and gives origin to G. conglobatus in Zone PL1.

Most likely ancestor: Globigerinoides obliquus - at confidence level 4 (out of 5). Data source: Stainbank et al. 2018;.

Biostratigraphic distribution

Geological Range:
Notes: From Subzone M13a to Holocene.
Last occurrence (top): within Holocene Epoch (0.00-0.01Ma, top in "Holocene" stage). Data source: Stainbank et al. 2018
First occurrence (base): within M13a subzone (8.58-9.83Ma, base in Tortonian stage). Data source: Stainbank et al. 2018

Plot of occurrence data:

Primary source for this page: Stainbank et al. 2018

References:

Aze, T. et al. (2011). A phylogeny of Cenozoic macroperforate planktonic foraminifera from fossil data. Biological Reviews. 86: 900-927. gs

Bé, A. W. H. & Tolderlund, D. S. (1971). Distribution and ecology of living planktonic foraminifera in surface waters of the Atlantic and Indian Oceans. In, Funnell, B. M. & Riedel, W. R. (eds) Micropaleontology of Oceans. Cambridge Univ. Press, Cambridge, UK 105-149. gs

Fordham, B. G. (1979). A chronocladogeny and corresponding classification of Neogene planktic foraminifera with a documentation of morphotypes from two Pacific deepsea stratigraphic sections. PhD thesis, University of Queensland, Australia. -. gs

Hemleben, C., Olsson, R. K., Premec Fucek, V. & Hernitz Kucenjak, M. (2018). Wall textures of normal perforate Oligocene planktonic foraminifera. 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 3): 55-78. gs

Rillo, M. C. (2016). Dataset: Henry Buckley collection of planktonic foraminifera. Natural History Museum Data Portal (data.nhm.a- c.uk). HREF="https://doi.org/10.5519/0035055">https://doi.org/10.5519/0035055. . -. gs

Stainbank, S., Spezzaferri, S., Kroon, D., de Leau, E. S. & Rüggeberg, A. (2018). The Planktonic foraminifera Globigerinoides eoconglobatus n. sp. in a glacial–interglacial context: IODP359 Sites U1467 and U1468. Swiss Journal of Geosciences. 111(3): 511-522. gs


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Globigerinoides eoconglobatus compiled by the pforams@mikrotax project team viewed: 14-11-2019

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