pforams@mikrotax - Subbotina senni pforams@mikrotax - Subbotina senni

Subbotina senni

Classification: pf_cenozoic -> Globigerinidae -> Subbotina -> Subbotina senni
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.


Citation: Subbotina senni (Beckmann 1953)
taxonomic rank: Species
Basionym: Sphaeroidinella senni
Taxonomic discussion: The thick calcite crust led Beckmann (1953) to place his new species senni in the genus Sphaeroidinella. Better understanding of the stratigraphic range of planktonic foraminifera, leading to the first detailed zonation of Paleogene and Neogene sections in Trinidad by Bolli (1957) showed that Sphaeroidinella was a Neogene genus. Bolli placed Beckmann’s species in Globigerina and showed that it had a lower to middle Eocene range. Subsequently, senni has been placed in Globigerinatheka (Fleisher, 1974), tentatively in Subbotina (Poore and Brabb, 1977), and in Muricoglobigerina (Blow, 1979). Bolli (1972) noted (fide Beckmann, 1971) the affinity of the thick wall structure of Globigerina senni with Globigerinatheka subconglobata micra (Shutskaya), thereby suggesting that the two species were phylogenetically related. Forms identified as G. micra are small, heavily encrusted, and lack identifiable supplementary apertures. Lacking type material, we suggest that these forms are small senni and that micra may be a junior synonym. Globigerina orbiformis Cole (a paratype here illustrated in SEM, Pl. 6.17, Figs. 5-7) may be a senior synonym but it appears not well enough preserved to make a positive determination and it has rarely been recorded in the literature.
Fleisher (1974) noted in his study of senni from the middle Eocene at DSDP Site 219, Arabian Sea, that this species may be the direct ancestor of G. micra due to the thickened crust-like wall and compact test, although he did not identify G. micra at Site 219. He placed senni in Globigerinatheka, rather than in Subbotina, due to the closer morphologic affinity of senni to this genus, even though the species lacks accessory apertures, a diagnostic feature of Globigerinatheka. Fleisher (1974) described Subbotina kiersteadae from the same section in which he identified senni and regarded it as the ancestral species of G. senni. The holotype of S. kiersteadae (Pl.6.17, Fig. 16) is a specimen from which the ultimate chamber is broken off. When present it would have covered the umbilical aperture as in senni. The test wall shows the typical encrustation of senni surrounding the umbilicus. It is here regarded as a junior synonym of senni. At Site 219 Fleisher recorded S. kiersteadae in Zones E8 and E9, along with G. senni.
Blow (1979) erected the genus Muricoglobigerina with Muricoglobigerina soldadoensis soldadoensis ( =Acarinina soldadoensis in this work) as the type species. The diagnostic feature of Blow’s new genus was the ‘murical-sheath’, which he described as due to the coalescence of muricae (individual conical projections or pustules from the chamber wall). He emphasized that the murical-sheath was a primary structure and could not be considered as a “calcite crust” (1979, p. 412) or secondary structure caused by late-stage calcification. Acarininid taxa with murical-sheaths were placed in Muricoglobigerina, whereas acarininid taxa with individual, separated muricae (pustules) covering the chamber walls were placed in Globorotalia (Acarinina). Furthermore, Blow regarded Muricoglobigerina soldadoensis as directly ancestral to Muricoglobigerina senni and used specimens identified as senni to illustrate the murical-sheath. However most of the specimens illustrated by Blow as Muricoglobigerina senni are not this species, as it is clear from his images (his pls. 131, 142, 146, 236) that he selected heavily pustulose acarininid specimens in an effort to demonstrate a relationship between these two species.
In Acarinina pustules continue to enlarge and coalesce during chamber growth and can form a dense compact structure (the murical-sheath of Blow) in some species. However, the thick wall of senni is due to an additional layer or layers of calcite, thus forming a calcite crust feature in the terminal stage of its life cycle. This can be observed in Plate 6.17, Figs. 9, 10 that show calcification around spines and in Figs. 19, 20 where it can be observed that spines were completely buried by late-stage calcification. This feature can be often observed in extant species (Neoglobigerina dutertrei, Sphaeroidinella dehiscens, deep-water Globorotalia etc., Hemleben and others, 1989).
This enigmatic species possesses the gross morphology of Subbotina. Globular chambers are arranged in a coil around a small umbilicus, the aperture is umbilically directed, and the aperture is a small arch, although without a distinct lip, bordered by a thin rim. Thickening of the test wall by late-stage gametogenetic calcification is not unusual in Eocene species of Subbotina and extension of the ultimate chamber over the umbilicus is also seen in the species S. angiporoides, S. jacksonensis, and S. utilisindex. [Olsson et al. 2006]

Catalog entries: Sphaeroidinella senni

Type images:

Distinguishing features:
Parent taxon (Subbotina): Low trochospiral, tripartite test, with 3-4 rapidly inflating, globular chambers in final whorl. Umbilicus nearly closed by tight coiling. Wall cancellate with spines at nodes of the ridges, +/- spine collars.
This taxon: Globular moderately elevated trochospiral test. Thick calcite crust covers and closes pores, and surrounds the umbilicus.

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.


Test trochospiral, moderately elevated initial whorl, globular, ovate to circular in outline, chambers ovoid; in spiral view 4 globular, slightly embracing chambers in ultimate whorl,increasing slowly in size, ultimate chamber may be equal to or smaller in size than penultimate chamber, sutures moderately depressed, straight; in umbilical view 3½ - 4 globular, slightly embracing chambers, increasing moderately in size, ultimate chamber may be equal to or smaller in size than penultimate chamber, sutures moderately depressed, straight; umbilicus small, surrounded by heavy buildup of calcite crust, aperture (when visible) umbilical, bordered by thickened rim; in edge view moderately elevated trochospire, chambers ovoid in shape, angled towards the umbilicus, somewhat embracing. [Olsson et al. 2006]

Wall type:
Normal perforate, cancellate, spinose, sacculifer-type wall, in adult or terminal stage covered by a thick calcite crust that closes off pores and buries spines. [Olsson et al. 2006]

Maximum diameter 0.28-0.42 mm. [Olsson et al. 2006]

Character matrix
test outline:Circularchamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical
sp chamber shape:Globularcoiling axis:Low-moderateperiphery:N/Aaperture border:Thick lip
umb chbr shape:Globularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Moderately depressedumb depth:Deepwall texture:Spinoseshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Moderately depressedfinal-whorl chambers:4-4 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology

Geographic distribution

Global in low to mid latitudes. [Olsson et al. 2006]
Aze et al. 2011 summary: Low to middle latitudes; based on Olsson et al. (2006a)

Isotope paleobiology
Subbotina senni apparently occupied a mixed layer habitat (Pearson and others, 1993, 2001). It records more negative δ18O values than do species of Catapsydrax, Hantkenina, and other species of Subbotina. It is less enriched in δ13C values than species of Acarinina and Morozovella. Subbotina senni may have been a shallow mixed layer species that sank to middle mixed layer or deeper depths during gametogenesis. The isotope values may display a shallow life style during the juvenile through preadult stage and adding a calcite crust below the thermocline (Pearson and others, 1993). [Olsson et al. 2006]
Aze et al. 2011 ecogroup 5 - High-latitude. Based on occurrence predominantly in high-latitude sites. Sources cited by Aze et al. 2011 (appendix S3): Pearson et al. (1993, 2001a); Coxall et al. (2000)

Phylogenetic relations
The origin of Subbotina senni is uncertain but we suggest that S. roesnaesensis is the most likely ancestor. Subbotina senni has been suggested by Bolli (1972) as an ancestor to the genus Globigerinatheka. Blow (1979) thought that it might be an ancestor to Globigerinatheka index. Following observations of wall texture and dissected specimens of senni, Guembelitroides nuttalli and globigerinathekides, we conclude that the most likely ancestor of Globigerinatheka is G. nuttalli (see Chapter 7). [Olsson et al. 2006]

Most likely ancestor: Subbotina roesnaesensis - at confidence level 4 (out of 5). Data source: Olsson et al. 2006 f6.2.

Biostratigraphic distribution

Geological Range:
Notes: Zone E6 to Zone E13. [Olsson et al. 2006]
Last occurrence (top): within E13 zone (37.99-39.97Ma, top in Bartonian stage). Data source: Eocene Atlas
First occurrence (base): within E6 zone (50.2-50.67Ma, base in Ypresian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Olsson et al. 2006 - Eocene Atlas, chap. 6, p. 159


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Subbotina senni compiled by the pforams@mikrotax project team viewed: 4-12-2023

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