Cassigerinelloita amekiensis


Classification: pf_cenozoic -> microperforate -> Guembelitriidae -> Cassigerinelloita -> Cassigerinelloita amekiensis
Sister taxa: C. amekiensis, C. sp.,

Taxonomy

Citation: Cassigerinelloita amekiensis Stolk 1965
Rank: Species
Basionym: Cassigerinelloita amekiensis
Synonyms:
Taxonomic discussion: This distinctive form has often been overlooked in biostratigraphic studies because of its small test size. Its relatively short stratigraphic range in the lower middle Eocene makes it a valuable biomarker, particularly for correlation of southern high latitude sites, where it occurs abundantly. [Huber et al. 2006]

Catalog entries: Cassigerinelloita amekiensis;

Type images:

Short diagnosis: Characterized by small, subglobular test with a rotating triserial axis of coiling, indistinguishable umbilicus and often indistinguishable primary aperture.

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.

Description


Diagnostic characters: Characterized by small, subglobular test with a rotating triserial axis of coiling, indistinguishable umbilicus and often indistinguishable primary aperture. [Huber et al. 2006]

Wall type: Microperforate, with micropores ranging from 0.5 to 1.0 mm diameter, finely to moderately pustulose, pustules on final one to two chambers, wall thicker on earlier chambers than penultimate and ultimate chambers. [Huber et al. 2006]

Test morphology: Test small, polygonal, subspherical, lacking a true umbilicus; chambers arranged in a series of very low triserial whorls that are coiled so that the test has two distinct coiling axes, increasing rapidly in size, six to eight chambers visible on the outside coils, eight to ten comprising adult tests; sutures moderately depressed; primary aperture visible in most but not all specimens, interiomarginal, semicircular or low-arched, with or without a thin lip, generally located across the suture between the penultimate and antepenultimate chambers; supplementary apertures may be present on the opposite side of the chamber with the primary aperture or on earlier chambers. [Huber et al. 2006]

Size: Holotype, maximum diameter 0.13 mm; general size range 0.07 to 0.14 mm. [Huber et al. 2006]

Character matrix

test outline:Lobatechamber arrangement:Triserialedge view:Inequally biconvexaperture:Interiomarginal
umb chamber shape:Globularcoiling axis:Lowperiphery:N/Aaperture border:Thin lip
sp chbr shape:Globularumbilicus:N/Aperiph margin shape:Broadly roundedaccessory apertures:Umbilical
umbilical or test sutures:Strongly depressedumb depth:N/Awall texture:Finely pustuloseshell porosity:Microperforate: <1µm
spiral sutures:Strongly depresseddiameter mm:0.13width mm:breadth mm:
final-whorl chambers:4.0-6.0

Biogeography and Palaeobiology


Geographic distribution: Li and Radford (1992) suggest C. amekiensis preferred inhabiting cool, unstable environments, such as zones of upwelling and southern high latitude surface waters. Its limited occurrence at low latitudes (e.g., Nigeria and Tanzania) may be a consequence of its preference for shelf environments or an artifact of having been overlooked because of its small test size. [Huber et al. 2006]

Isotope paleobiology: No data available. [Huber et al. 2006]

Phylogenetic relations: On the basis of similarity in wall texture, coiling, and the interiomarginal aperture as well as stratigraphic overlap, Li and Radford (1992) suggested that C. amekiensis probably descended from Jenkinsina triseriata following a change from unidirectional triserial coiling to an offset, rotating triserial coiling. [Huber et al. 2006]

Most likely ancestor: Jenkinsina columbiana - at confidence level 0 (out of 5). Data source: Hubwr et al. 2006, f6.

Biostratigraphic distribution

Geological Range:
Notes: Upper lower - lower Eocene; Zone E7 to Zone E9 at lower latitudes, nominate taxon for the Cassigerinelloita amekiensis Taxon Range Zone (AE4) at southern high latitudes. First recorded in the uppermost(?) lower Eocene to middle Eocene in the Bende Ameki Group in eastern Nigeria (Stolk, 1965), and found to range into upper Zone E9 in southeastern Tanzania, Tanzania Drilling Projet, Site 13, with its highest occurrence observed just below the highest occurrence of Morozovella aragonensis (P. N. Pearson, unpublished data). At most southern high latitude sites, the HO of C. amekiensis is recorded at the same level as or just above the FO of Guembelitria triseriata (Nocchi and others, 1991; Li and Radford, 1992). Although Huber (1991) reported the reverse to apply at Site 738, re-examination of samples from that site revealed that the HO of J. triseriata is at the same level as the LO of C. amekiensis (Huber and Quille_ve_re_, 2005). Its range is diachronous between low and high latitudes, its first occurrence is slightly earlier at southern high latitudes, whereas its last occurrence is later at low latitudes. [Huber et al. 2006]
Last occurrence (top): within E9 zone (43.23-43.85Ma, top in Lutetian stage). Data source: Eocene Atlas
First occurrence (base): within E7 zone (45.72-50.20Ma, base in Ypresian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Huber et al. 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 16, p. 471

References:

Huber, B.T., (1991). Paleogene and early Neogene planktonic foraminifer biostratigraphy of ODP Leg 119 Sites 738 and 744, Kerguelen Plateau (southern Indian Ocean). Proceedings of the Ocean Drilling Program, Scientific Results, 119: 427-449.

Huber, B.T., (1991). Paleocene and Early Neogene Planktonic Foraminifer Biostratigraphy of Sites 738 and 744, Kerguelen Plateau (Southern Indian Ocean). Proceedings of the Ocean Drilling Program, Scientific Results, 119: 427-449.

Huber, B.T.; Olsson, R.K. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene microperforate planktonic foraminifera (Jenkinsina, Cassigerinelloita, Chiloguembelina, Streptochilus, Zeauvigerina, Tenuitella, and Cassigerinella) and Problematica (Dipsidripella). In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera, Cushman Foundation Special Publication 41. Cushman Foundation Special Publication. Allen Press, Lawrence, Kansas, pp. 461-508.

Li, Q. & Radford, S.S., (1992). Morphology and affinity of the planktonic foraminifer Cassigerinelloita amekiensis Stolk and reclassification of Cassigerinelloita Stolk. In: Wise, S.W.J., Schlich, R. and al., e. (Editors), Proceedings of the Ocean Drilling Program, Scientific Results. Ocean Drilling Program, College Station, Texas, pp. 595-602.

Nocchi, M.; Amici, E. & Premoli Silva, I., (1991). Planktonic foraminiferal biostratigraphy and paleoenvironmental interpretation of Paleogene faunas from the subantarctic transect, Leg 114. In: Ciesielski, P.F., Kristoffersen, Y. and al., e. (Editors), Proceedings of the Ocean Drilling Program, Scientific Results. Ocean Drilling Program, College Station, Texas, pp. 233-273.

Stolk, J., (1965). Contibution à l'étude des corrélations microfaunique do Tertiaire inférieur de la Nigèrie méridionale. Bureau Recherches Géologiques Minerales Mémoire, 32: 247-267.

Stott, L.D. & Kennett, J.P., (1990). The Paleoceanographic and Paleoclimatic signature of the Cretaceous/Paleogene boundary in the Antarctic: Stable isotopic results from ODP Leg 113. Proceedings of the Ocean Drilling Program, Scientific Results, 113: 829-848.


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Cassigerinelloita amekiensis compiled by the pforams@mikrotax project team viewed: 19-11-2017

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