Pseudohastigerina micra

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


Citation: Pseudohastigerina micra (Cole 1927)
Rank: Species
Basionym: Nonion micrus Cole 1927
Taxonomic discussion: Pseudohastigerina micra is common in the upper Eocene but it declined dramatically in size and abundance at the Eocene/Oligocene boundary (Cordey and others, 1970; Keller, 1985, Nocchi and others, 1986; Miller and others, 2008; Wade and Pearson, 2008).  The disappearance of large-sized P. micra can be used to correlate the Eocene/Oligocene boundary proper, especially when hantkeninids are rare or absent (Miller and others, 2008; Wade and Pearson, 2008). [Pearson et al. 2018]

Pseudohastigerina danvillensis (Howe and Wallace) was described from the Jackson Formation at Danville Landing on the Ouachita River, Lousiana. The Jackson Formation at this locality can be placed in Zone E15-16 based on the occurrence of Cribrohantkenina inflata (Howe). Blow (1979) recognized P. danvillensis, which has been treated as a junior synonym of Pseudohastigerina micra (Cole), as a valid species distinguishable from P. micra. Although he stated that he had examined type material from Danville Landing given to him by Ruth Todd, he did not illustrate any specimens from this locality. Most of the specimens he illustrated by SEM were from Zone E8 in deep-sea piston core KANE 9-Core 42 from the Endeavour Seamount, equatorial Atlantic Ocean. He illustrated other specimens that he identified as P.
danvillensis from Zones E9 and E16 from localities in Tanzania. Blow emphasized that P. danvillensis could be separated from P. micra on the basis of a more compressed chambers, ovoid or ogyval-shaped chambers in edge view, and recurved sutures. However, the holotype of P. danvillensis (Pl.14.3, Figs. 13, 14) has rounded, inflated chambers as does the holotype of P. micra (Pl.14.3, Figs. 11, 12) and the ultimate chamber of the P. micra holotype is more ovoid in appearance. Furthermore, the topotype of P. micra figured in Blow (1979, pl. 253, fig. 7) is nearly identical to P. danvillensis holotype (Pl.14.3, Figs. 13, 14) and the two holotypes of these species are similar in umbilical view (compare Pl. 14.3: Figs. 11 and 13) except for the ultimate chambers which differ slightly in their dimensions. The sutures in both holotypes are depressed and radial between earlier chambers of the final whorl and are slightly curved distally between the ultimate and penultimate chambers. The ultimate chamber of P. danvillensis holotype has bipartite apertures, a characteristic feature seen in populations of P. micra, although, curiously, the bipartite apertures are situated below a single arched thickened lip. Thus, Blow’s criteria for separating these two species cannot be applied to the two holotypes and P. danvillensis is placed as a junior synonym of P. micra.  [Olsson & Hemleben 2006]

Pseudohastigerina acutimarginata, P. pellucida, and P. quadrata were described by Abdel-Kareem (1979) from the middle Eocene of Egypt. The three species are considered junior synonyms of P. micra as they show the range of morphologic variability observed in this species. Pseudohastigerina sharkriverensis Berggren and Olsson figured by Warraich and Ogasawara (2001, figs. 16, 18, 19) does not exhibit the quadrate outline of P. sharkriverensis and is regarded here as P. micra. It is from the same sample as the specimen identified by them as P. micra (their figs. 16, 18, 19). [Olsson & Hemleben 2006]

Catalog entries: Nonion micrus, Nonion danvillensis, Nonion iota, Pseudohastigerina acutimarginata, Pseudohastigerina pellucida, Pseudohastigerina quadrata

Type images:

Distinguishing features: Tests small, compressed, nearly circular in outline. Chambers globular, straight sutures, and rounded periphery in edge view. Aperture, high circular arch,with narrow, well-developed lip, frequently bipartite.

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.


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

Size: Maximum diameter of holotype 0.17 mm, thickness 0.09 mm. [Olsson & Hemleben 2006]

Character matrix

test outline:Subcircularchamber arrangement:Planispiraledge view:Equally biconvexaperture:Equatorial
sp chamber shape:Globularcoiling axis:N/Aperiphery:N/Aaperture border:Thin lip
umb chbr shape:Globularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:Sutural
spiral sutures:Strongly depressedumb depth:Shallowwall texture:Smoothshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:5.0-6.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology

Geographic distribution: Global in low to high latitudes. [Olsson & Hemleben 2006]
Aze et al. 2011 summary: Low to high latitudes; based on Olsson & Hemleben (2006)

Isotope paleobiology: Usually registers among the most negative ∂18O values of assemblages, indicating a shallow water habitat. However carbon isotope are strongly depleted with respect to the surface dwelling muricate species, suggesting a different carbon metabolism from other surface dwellers (Poore and Matthews, 1984; Boersma and others, 1987; Pearson and others, 2001). [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): Poore & Matthews (1984); Boersma et al. (1987); Pearson et al. (2001a)

Phylogenetic relations: Pseudohastigerina micra evolved from Pseudohastigerina wilcoxensis by a reduction in size of the test, by a reduction in rate of increase in the size of chambers, and by an increase in number of chambers in the final whorl. [Olsson & Hemleben 2006]

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

Biostratigraphic distribution

Geological Range:
Notes: Zone E7 (Olsson and Hemleben, 2006) to Zone O1 (Keller, 1985; Nocchi and others, 1986; Leckie and others, 1993; Pearson and Chaisson, 1997; Wade and Pearson, 2008). The species is typically rare in Zone O1 and it is unclear how far through the zone the range extends. The highest occurrence we have confirmed is from the middle of Zone O1 (Leckie and others, 1993, pl. 6, fig. 20; recorded as Pseudohastigerina aff. P. micra).
Last occurrence (top): within O1 zone (32.10-33.90Ma, top in Rupelian stage). Data source: Olsson & Hemleben (2006) fig 14.1
First occurrence (base): in mid part of E7a subzone (50% up, 49.3Ma, in Ypresian stage). Data source: Olsson & Hemleben (2006) fig 14.1

Plot of occurrence data:

Primary source for this page: Pearson et al. 2018 - Olig Atlas chap.14 p.405; Olsson & Hemleben 2006 - Eocene Atlas, chap. 14, p. 422


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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


Pseudohastigerina micra compiled by the pforams@mikrotax project team viewed: 22-10-2020

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