Pseudohastigerina sharkriverensis


Classification: pf_cenozoic -> Globanomalidae -> Pseudohastigerina -> Pseudohastigerina sharkriverensis
Sister taxa: P. naguewichiensis, P. micra, P. sharkriverensis, P. wilcoxensis, P. sp.,

Taxonomy

Citation: Pseudohastigerina sharkriverensis Berggren and Olsson 1967
Rank: Species
Basionym: Pseudohastigerina sharkriverensis
Synonyms:
Taxonomic discussion: This species has not been widely recorded in the published literature, which may in part be due to its mid-latitude biogeographic restriction. The only discussion of the species was by Blow (1979) who stated (p. 1192) “In the writer’s view, the production of the sharkriverensis-morphotype is a strict allometric and orthogenetic development of the wilcoxensis-morphotypes to the limits imposed by the geometry of planispirally coiled forms with inflated chambers”. He apparently based his opinion on his belief that the development of a bipartite apertural system was due to a tightening of the chamber coil and greater inflation of chambers that first occurred in P. wilcoxensis. However, bipartite apertures are also seen in Pseudohastigerina micra (Cole) which has much compressed chambers, so that bipartite apertures appear to be a feature of the Pseudohastigerina group of species. The evolution of P. sharkriverensis from P. wilcoxensis can not be regarded as strictly an allometric development because there is a change in chamber shape.
Blow suggested that Biglobigerinella kerisensis Suleymanov (1966) might be a senior synonym of P. sharkriverensis. Biglobigerinella kerisensis was described from the upper Eocene of Kizil Kum, central Asia of the former Soviet Union. Scanning electron micrographs of the holotype of this species (Pl.14.4, Figs. 13-15) show a deformed specimen with an asymmetrical ultimate chamber which extends over and obscures the umbilical area of one side. Although the specimen appears to be planispiral, it is difficult to make a meaningful morphological comparison with P. sharkriverensis without additional specimens. Since P. sharkriverensis is not known to range above the middle Eocene and B. kerisensis is poorly known and not well documented, it is advisable to use the former name. Globigerinella pseudovoluta Bandy (1949) was also mentioned by Blow as a possible senior synonym of P. sharkriverensis but this species is more properly placed in P. wilcoxensis because the chambers are more
compressed in edge view, the aperture is highly arched, and there is a regular increase in chamber size, all typical features of P. wilcoxensis. [Olsson & Hemleben 2006]

Catalog entries: Pseudohastigerina sharkriverensis

Type images:

Distinguishing features: Test large, oval to quadrate; chambers much inflated, globular. Low chamber growth in final 3 chambers bipartite apertures common.

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: Pseudohastigerina sharkriverensis is characterized by its large oval to quadrate test, much inflated globular chambers, the slower chamber growth in the final 3 chambers and the common development of bipartite apertures in the final chamber. In edge view the chambers are much inflated in contrast to the more compressed chambers in P. wilcoxensis. [Olsson & Hemleben 2006]

Wall type: Smooth, normal perforate. [Olsson & Hemleben 2006]

Test morphology: Test planispiral, compressed, tightly coiled, involute, oval to quadrate in outline, slightly lobulate, chambers, inflated, globular; in umbilical view 6 chambers in ultimate whorl with the final 3 composing about two thirds of the test size, first 4 chambers increasing rapidly in size and the final 2 chambers more gradually in size, ultimate chamber sometimes slightly reduced in size, sutures moderately depressed, straight to slightly curved, umbilicus small, circular in shape; in edge view chambers much inflated, oval to nearly circular in outline, primary aperture an oval low arch, bordered by a narrow lip, bipartite apertures a common feature in adult specimens, test compressed with a rounded periphery; peripheral margin perforate. [Olsson & Hemleben 2006]

Size: Maximum diameter of holotype 0.35 mm, thickness 0.20 mm. [Olsson & Hemleben 2006]

Character matrix

test outline:Quadratechamber arrangement:Planispiraledge view:Equally biconvexaperture:Biapertural
sp chamber shape:Inflatedcoiling axis:N/Aperiphery:N/Aaperture border:Thin lip
umb chbr shape:Inflatedumbilicus:Narrowperiph margin shape:Moderately roundedaccessory apertures:Intralaminal
spiral sutures:Moderately depressedumb depth:Shallowwall texture:Smoothshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Moderately depressedfinal-whorl chambers:5.5-6.5 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Apparently restricted distribution in mid latitudes. [Olsson & Hemleben 2006]
Aze et al. 2011 summary: Middle latitudes only; based on Olsson & Hemleben (2006)

Isotope paleobiology: No data available. [Olsson & Hemleben 2006]
Aze et al. 2011 ecogroup 2 - Open ocean mixed-layer tropical/subtropical, without symbionts. Based on δ13C lighter than species with symbionts; also with relatively light δ18O. Sources cited by Aze et al. 2011 (appendix S3): this study

Phylogenetic relations: Pseudohastigerina sharkriverensis evolved from P. wilcoxensis by an increase in size of the test, a slowly of chamber size increase in the last few chambers of the ultimate whorl, and by a change in chamber shape from compressed to globular inflated chambers. The aperture is reduced to a low arch in the transition. [Olsson & Hemleben 2006]

Most likely ancestor: Pseudohastigerina wilcoxensis - at confidence level 4 (out of 5). Data source: Olsson & Hemleben (2006) fig 14.1.

Biostratigraphic distribution

Geological Range:
Notes: Middle Eocene, Zone E7? to Zone E13? [Olsson & Hemleben 2006 ]
Last occurrence (top): within E13 zone (37.99-39.97Ma, top in Bartonian stage). Data source: Olsson & Hemleben (2006) fig 14.1
First occurrence (base): within E7a subzone (48.31-50.20Ma, base in Ypresian stage). Data source: Olsson & Hemleben (2006) fig 14.1

Plot of occurrence data:

Primary source for this page: Olsson & Hemleben 2006 - Eocene Atlas, chap. 14, p. 426

References:

Bandy, O. L. (1949). Eocene and Oligocene foraminifera from Little Stave Creek, Clarke County, Alabama. Bulletin of American Paleontology. 32(131): 1-210. gs

Berggren, W. A., Olsson, R. K. & Reyment, R. A. (1967). Origin and development of the foraminiferal genus Pseudohastigerina Banner and Blow, 1959. Micropaleontology. 13(3): 265-288. gs

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

McKeel, D. R. & Lipps, J. H. (1972). Calcareous plankton from the Tertiary of Oregon. Palaeogeography, Palaeoclimatology, Palaeoecology. 12(01-Feb): 75-93. gs

Olsson, R. K. & Hemleben, C. (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Globanomalina, Planoglobanomalina n. gen and Pseudohastigerina. 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 14): 413-432. gs

Suleymanov, I. S. (1966). New upper Eocene species of the genus Biglobigerinella. Paleontologicheskiy Zhurnal. 1966(1): 148-149. gs

White, M. P. (1928). Some Index Foraminifera of the Tampico Embayment Area of Mexico. Journal of Paleontology. 2(3): 177-215. gs


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Pseudohastigerina sharkriverensis compiled by the pforams@mikrotax project team viewed: 12-11-2019

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