Subbotina minima


Classification: pf_cenozoic -> Globigerinidae -> Subbotina -> Subbotina minima
Sister taxa: S. projecta, S. tecta, S. jacksonensis, S. corpulenta, S. eocaena, S. gortanii, S. crociapertura, S. yeguaensis, S. senni, S. roesnaesensis, S. utilisindex, S. angiporoides, S. minima, S. linaperta, S. patagonica, S. cancellata, S. hornibrooki, S. velascoensis, S. triloculinoides, S. triangularis, S. trivialis, S. sp.,

Taxonomy

Citation: Subbotina minima (Jenkins, 1965)
Rank: species
Basionym: Globigerina angiporoides minima Jenkins, 1965
Synonyms:
Taxonomic discussion:

Subbotina minima (Jenkins) was considered a junior synonym of Subbotina angiporoides (Hornibrook) by Olsson and others (2006). However, in our investigations of new material from the equatorial Pacific Ocean IODP Site U1334, we frequently find forms with a more open umbilicus and less compact test, which are much more typical of S. minima than with S. angiporoides. We therefore recognize S. minima as a distinct morphospecies. [Wade et al. 2018]

Jenkins (1965) suggested that S. minima is smaller than S. angiporoides and that this is a helpful characteristic for distinguishing between the two species. However, given the variability of illustrated specimens, we have not found this to be a particularly useful diagnostic feature and any size difference between the two species is subtle. [Wade et al. 2018]

In our opinion, one of the paratype specimens (Olsson and others, 2006, pl. 6.6, fig. 5) of S. angiporoides has a more lobate periphery and open umbilicus consistent with S. minima. Also, two of the paratype specimens illustrated by Jenkins as Globigerina angiporoides minima (1965, pl. 7, figs. 55, 56) share morphological characteristics, specifically a much tighter coiling mode and embracing final chamber, more similar to S. angiporoides. [Wade et al. 2018]

Catalog entries: Globigerina angiporoides minima

Type images:

Distinguishing features: Like S. linaperta but chambers do not increase rapidly in size, hence outline triangular

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 minima has a “reuleaux” (inflated) triangular outline, particularly evident in spiral view. It is distinguished from Subbotina angiporoides by its less compact test, more open, not slit-like aperture, common absence of the kummerform final chamber and less distinct lip. It is distinguished from S. linaperta by lacking compressed chambers that increase rapidly in size and from S. utilisindex by its less compact triangular test and 3½-4 chambers in the final whorl. [Wade et al. 2018] 


Wall type: Spinose, normal perforate, moderately cancellate, often thickened by addition of gametogenetic calcite, ruber/sacculifer-type wall.

Test morphology: Test small to moderate size, umbilicus small, open, low trochospiral, “reuleaux” triangular in shape, axial periphery rounded; chambers globular, embracing, increasing slowly in size, 10-12 chambers coiled in 2 whorls, 3½-4 chambers in the final whorl; sutures weakly depressed, radial to slightly curved; aperture a low arch, umbilical to extraumbilical, bordered by a lip. [Wade et al. 2018]

Size: Maximum diameter of holotype 0.37 mm. [Wade et al. 2018]

Character matrix

test outline:Triangularchamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical
sp chamber shape:Globularcoiling axis:Lowperiphery:N/Aaperture border:Thin lip
umb chbr shape:Globularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Weakly depressedumb depth:Shallowwall texture:Spinoseshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Weakly depressedfinal-whorl chambers:3.5-4.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Common in high southern latitudes; probably cosmopolitan, although, so far no records in high northern latitudes. [Wade et al. 2018]

Isotope paleobiology: Multispecies stable isotope investigations from Site U1334 indicate that Subbotina minima calcifies in the thermocline. This species records more negative δ18O values in comparison to co-occurring S. utilisindex (Moore and others, 2014). [Wade et al. 2018]

Phylogenetic relations: Subbotina minima descended from S. linaperta in the middle Eocene and subsequently gave rise to S. angiporoides (Jenkins, 1965). [Wade et al. 2018]

Most likely ancestor: Subbotina linaperta - at confidence level 4 (out of 5). Data source: Wade et al. 2018.
Likely descendants: Subbotina angiporoides;

Biostratigraphic distribution

Geological Range:
Notes: The range of S. minima is poorly constrained. It is described from the upper part of the middle Eocene. In the Gulf of Mexico, Spezzaferri and Premoli Silva (1991) found its extinction lower within Zone O3 than its descendant S. angiporoides. [Wade et al. 2018]
Last occurrence (top): within O3 zone (29.18-30.28Ma, top in Rupelian stage). Data source:
First occurrence (base): within Bartonian Stage (37.75-41.15Ma, base in Bartonian stage). Data source: Wade et al. 2018 (very poorly constrained

Plot of occurrence data:

Primary source for this page: Wade et al. 2018 - Olig Atlas chap.10 p.321

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

Hornibrook, N. d. B. (1965). Globigerina angiporoides n. sp. from the Upper Eocene and Lower Oligocene of New Zealand and the status of Globigerina angipora Stache, 1865. New Zealand Journal of Geology and Geophysics. 8(5): 834-838. gs

Jenkins, D. G. (1965b). Planktonic Foraminiferal zones and new taxa from the Danian to lower Miocene of New Zealand. New Zealand Journal of Geology and Geophysics. 8(6): 1088-1126. gs

Jenkins, D. G. (1971). New Zealand Cenozoic Planktonic Foraminifera. New Zealand Geological Survey, Paleontological Bulletin. 42: 1-278. gs

Li, Q., McGowran, B. & James, N. P. (2003b). Eocene–Oligocene planktonic forminiferal biostratigraphy of Sites 1126, 1130, 1132, and 1134, ODP Leg 182, Great Australian Bight. Proceedings of the Ocean Drilling Program, Scientific Results. 182: 1-28. gs

Moore, T. C. et al. (2014). Equatorial Pacific Productivity Changes near the Eocene-Oligocene Boundary. Paleoceanography. 29: 825-844. gs

Nocchi, M., Amici, E. & Premoli Silva, I. (1991). Planktonic foraminiferal biostratigraphy and paleoenvironmental interpretation of Paleogene faunas from the subantarctic transect, Leg 114. Proceedings of the Ocean Drilling Program, Scientific Results. 114: 233-273. gs

Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (2006b). Taxonomy, biostratigraphy, and phylogeny of Eocene Globigerina, Globoturborotalita, Subbotina, and Turborotalita. 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 6): 111-168. gs

Spezzaferri, S. & Premoli Silva, I. (1991). Oligocene planktonic foraminiferal biostratigraphy and paleoclimatic interpretation from Hole 538A, DSDP Leg 77, Gulf of Mexico. Palaeogeography, Palaeoclimatology, Palaeoecology. 83: 217-263. gs

Wade, B. S., Olsson, R. K., Pearson, P. N., Edgar, K. M. & Premoli Silva, I. (2018a). Taxonomy, biostratigraphy, and phylogeny of Oligocene Subbotina. 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 10): 307-330. gs


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Subbotina minima compiled by the pforams@mikrotax project team viewed: 17-10-2019

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Short stable page link: http://mikrotax.org/pforams/index.php?id=104370 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (1)

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Bridget Wade

Please add the holotype of minima. Oligocene Atlas page 310, plate 10.1, figs. 10-12

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Jeremy Young (UK)

thanks - the image was actually in the system but the link to the catalog entry was missing, it is in now, Jeremy

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