Parasubbotina inaequispira


Classification: pf_cenozoic -> Globigerinidae -> Parasubbotina -> Parasubbotina inaequispira
Sister taxa: P. griffinae, P. eoclava, P. hagni, P. prebetica, P. inaequispira, P. pseudowilsoni, P. variospira, P. varianta, P. pseudobulloides, P. aff. pseudobulloides, P. sp.,

Taxonomy

Citation: Parasubbotina inaequispira (Subbotina 1953)
Rank: Species
Basionym: Globigerina inaequispira
Synonyms:
Taxonomic discussion: The holotype of Parasubbotina inaequispira (Subbotina) is illustrated here in SEM for the first time (Pl.5.11, Figs. 1-3). Blow (1979, p. 1259) regarded P. inaequispira as ancestral to Subbotina crociapertura because of the tendency in P. inaequispira “to produce apertural systems with a slightly expanded to very slightly hooked distal part”, which he believed led to the distinctive hook-shaped aperture in S. crociapertura. However, the majority of specimens he illustrated to demonstrate this feature cannot be placed in P. inaequispira. In fact, Blow’s images of inaequispira show different types of wall texture that suggests mixing of separate species. The specimens of S. crociapertura from Tanzania illustrated by Blow, which includes the holotype, have a bulloides-type wall texture whereas P. inaequispira has a ruber/sacculifer-type wall texture. Some specimens of P. inaequispira illustrated by Blow (his pl. 177, fig. 3; pl. 180, figs. 2, 3; pl. 185, fig. 9) have a bulloides-type wall texture and may be morphotypes of S. crociapertura.
Of particular interest are Blow’s images of P. inaequispira from Zones E7 and E8 from the Endeavour Seamount in the North Atlantic Ocean (his pl. 151, figs. 5-7; pl. 163, figs. 4-10). These specimens show a fully developed, high porosity, reticulated, sacculifer-type wall texture that is characteristic of the genus Clavigerinella, which apparently first developed in P. inaequispira. Some of the specimens illustrated (his pl. 151, figs. 9 and 10) are placed in the intermediate species Parasubbotina eoclava Coxall, Huber, and Pearson that evolved from P. inaequispira and is believed to be directly ancestral to Clavigerinella.
The type material of Globigerina achtshacujmensis Khalilov and Globigerina inaequispira var. transversa Khalilov has been viewed by WAB and, despite the poor preservation, both are clearly synonyms of P. inaequispira. The holotype and three paratypes of Globigerina baylissi Samanta were viewed by PNP. Samanta distinguished his taxon from inaequispira by the supposed radial elongation of the final chamber, but this feature is poorly developed and falls within the range of variation here permitted to P. inaequispira. More markedly radially elongate parasubbotinids are assigned to P. eoclava Coxall, Huber and Pearson. [Olsson et al. 2006]

Catalog entries: Globigerina inaequispira, Globigerina inaequispira incluta, Globigerina inaequispira testata

Type images:

Distinguishing features: Test, lobulate, very low trochospiral, rather openly coiled, 4-4½ chambers in final whorl, which is much larger than inner whorl. Aperture anteriorly directed umbilical-extraumbilical, lacking thick 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: Subbotina (1953) alluded to the “Globigerinella-like” coiling style of her species and the small size of the inner whorl in comparison to the outer whorl, the latter feature lending the taxon its name. These features arise from the rapid rate of chamber expansion and their low and slightly irregular trochospiral arrangement, characters that help assign the species to the genus Parasubbotina. The species is distinguished by its lobulate, very low trochospiral test with 4-4½ chambers in the final whorl and its anteriorly directed umbilical-extraumbilical aperture.
The species has been widely identified in previous literature, but often incorrectly so. Parasubbotina inaequispira is distinguished from P. varianta by being more openly coiled and having less closely appressed chambers. It differs from Paragloborotalia griffinoides n. sp. principally in having much less dorso-ventral expansion and lacking the thick, prominent lip of that taxon. It differs from P. eoclava in lacking radially elongate chambers and a thick, flaring lip. [Olsson et al. 2006]

Wall type: Symmetrically to asymmetrically cancellate (initially ruber/sacculifer-type wall texture but becoming high porosity, reticulated sacculifer-type in adult morphology and particularly in stratigraphically younger morphotypes Clavigerinella-type with surface thickening), normal perforate, spinose. [Olsson et al. 2006]

Test morphology: Test very low trochospiral, globular, lobulate in outline, chambers globular; in spiral view 4-4½ globular, well separated chambers in final whorl, increasing moderately in size, sutures moderately depressed, straight, final chamber may be slightly reduced in size relative to the penultimate chamber; in umbilical view 4-4½ globular, well separated chambers, increasing moderately in size, sutures moderately depressed, straight, umbilicus a moderate sized opening, enclosed by surrounding chambers, aperture umbilical to somewhat extraumbilical and directed towards the anterior side of the test, bordered by a narrow continuous, lip, ultimate chamber may be slightly reduced in size relative to the penultimate chamber; in edge view chambers globular in shape, well separated, aperture visible as a low arch, bordered by a narrow lip. [Olsson et al. 2006]

Size: Maximum diameter of holotype 0.42 mm, thickness 0.28 mm. [Olsson et al. 2006]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Inflatedcoiling axis:Very lowperiphery:N/Aaperture border:Thin lip
umb chbr shape:Globularumbilicus:Wideperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Moderately depressedumb depth:Shallowwall texture:Cancellateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:4.0-4.5 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Global in low to mid latitudes. Parasubbotina. inaequispira is a common constituent of relatively high productivity environments in the Eocene. [Olsson et al. 2006]
Aze et al. 2011 summary: Low to middle latitudes and high productivity/upwelling; based on Olsson et al. (2006c)

Isotope paleobiology: Relatively heavy ∂18O indicating cool water (H. K. Coxall, unpublished data). [Olsson et al. 2006]
Aze et al. 2011 ecogroup 6 - Upwelling/high productivity. Based on occurrence predominantly in sites of high productivity or upwelling. Sources cited by Aze et al. 2011 (appendix S3): Pearson et al. (2001a); H. K. Coxall unpublished data

Phylogenetic relations: Parasubbotina inaequispira appears to have developed from P. varianta (Subbotina) in the earliest Eocene. In turn it gave rise to P. eoclava and P. griffinae in the latest early Eocene. [Olsson et al. 2006]

Most likely ancestor: Parasubbotina varianta - at confidence level 4 (out of 5). Data source: Olsson et al. 2006 f5.1.
Likely descendants: Guembelitrioides nuttalli; Parasubbotina eoclava; Parasubbotina griffinae; Parasubbotina prebetica;

Biostratigraphic distribution

Geological Range:
Notes: Zone E1 to Zone E8. [Olsson et al. 2006]
Last occurrence (top): within E8 zone (43.85-45.72Ma, top in Lutetian stage). Data source: Olsson et al. 2006
First occurrence (base): within E1 zone (55.81-55.96Ma, base in Ypresian stage). Data source: Olsson et al. 2006

Plot of occurrence data:

Primary source for this page: Olsson et al. 2006 - Eocene Atlas, chap. 5, p. 101

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

Khalilov, D. M. (1956). 0 pelagicheskoy faune foraminifer Paleogenovykh otlozheniy Azerbaydzhana [Pelagic Foraminifera of the Paleogene Deposits of the Azerbaizhan SSR]. Trudy Instituta Geologii, Akademiya Nauk Azerbaidzhanskoi SSR. 17: 234-255. gs

Kurgalimova, G. G. (1972). Описание некоторых характерных глобигерин из среднеэоценовых отложений Восточного Приаралья [Description of some characteristic globigerinids from Middle Eocene deposits of the Eastern Aral Sea region]. Paleontological collection, Proceedings of the All-Union Scientific Research Geological Prospecting Petroleum Institute (VNIGNI). 4(83): 109-115. gs

Olsson, R. K., Pearson, P. N. & Huber, B. T. (2006c). Taxonomy, biostratigraphy, and phylogeny of Eocene Catapsydrax, Globorotaloides, Guembelitrioides, Paragloborotalia, Parasubbotina, and Pseudoglobigerinella n. gen. 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 5): 67-110. gs

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

Stainforth, R. M., Lamb, J. L., Luterbacher, H., Beard, J. H. & Jeffords, R. M. (1975). Cenozoic planktonic foraminiferal zonation and characteristics of index forms. University of Kansas Paleontological Contributions. 62: 1-425. gs

Subbotina, N. N. (1953). Foraminiferes fossiles d'URSS Globigerinidae, Globorotaliidae, Hantkeninidae. Bureau de Recherches Geologiques et Minieres. 2239: 1-144. gs

Toumarkine, M. & Luterbacher, H. (1985). Paleocene and Eocene planktic foraminifera. In, Bolli, H. M. , Saunders, J. B. & Perch-Neilsen, K. (eds) Plankton Stratigraphy. Cambridge Univ. Press, Cambridge 87-154. gs

Warraich, M. Y. & Ogasawara, K. (2001). Tethyan Paleocene-Eocene planktic foraminifera from the Rakhi Nala and Zinda Pir land sections of the Sulaiman Range, Pakistan. Science Reports of the Institute of Geosciences, University of Tsukuba, Section B = Geological Sciences. 22: 1-59. gs

Warraich, M. Y., Ogasawara, K. & Nishi, H. (2000). Late Paleocene to early Eocene planktic foraminiferal blostratigraphy of the Dungan Formation, Sulaiman Range, central Pakistan. Paleontological Research. 4(4): 275-301, 218 figures, 273 aendices. gs


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Parasubbotina inaequispira compiled by the pforams@mikrotax project team viewed: 17-10-2019

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