Cassigerinelloita amekiensis Stolk 1965 from: Pearson, P.N.Olsson, R.K.Hemleben, C.Huber, B.T.Berggren, W.A. (2006): Atlas of Eocene Planktonic Foraminifera. p. 1-513 | . |
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Species Cassigerinelloita amekiensis Stolk 1965 |
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| Diagnosis / Definition: |
Pearson et al. (2006):
DESCRIPTION.
Type of wall: Microperforate, with micropores
ranging from 0.005 to 0.01 mm diameter, finely to
moderately pustulose, pustules on final one to two
chambers, wall thicker on earlier chambers than
penultimate and ultimate chambers.
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, 6-8 chambers visible on the
outside coils, 8-10 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.
Size: Holotype, maximum diameter 0.13 mm;
general size range 0.07-0.14 mm. |
| Discussion / Comments: |
Pearson et al. (2006):
DISTINGUISHING FEATURES-
Characterized by
small, subglobular test with a rotating triserial axis of
coiling, indistinguishable umbilicus and often
indistinguishable primary aperture.
DISCUSSI0N.- 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.
PHYLOGENETIC RELATIONSHIPS.-
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.
STRATIGRAPHIC RANGE.-
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 H0 of C. amekiensis is recorded at the same level as
or just above the F0 of Guemhelitria triseriata (Nocchi
and others, 1991; Li and Radford, 1992). Although Huber
(1991) reported the reverse to apply at Site 738, reexamination
of samples from that site revealed that the
H0 of J. triseriata is at the same level as the L0 of C.
amekiensis (Huber and Quillévéré, 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.
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.
STABLE ISOTOPE PALEOBIOL0GY.-
No data
available.
REPOSITORY.-
Musée Géologique Africain, Dakar,
Senegal. |
| Synonym list: |
Pearson et al. (2006):
1990 Globigerina sp. B . - Stott & Kennett : p.559 pl. 5; fig. 1-14 [lower-middle Eocene, ODP Site 689, Maud Rise,
Antarctica]
1991 Cassigerinelloita amekiensis Stolk. - Nocchi et al. : p.267 pl. 4; fig. 1-2 [lower middle Eocene
Zone PlO-ll, ODP Hole 703A, mid-Atlantic Ridge,
southern South Atlantic Ocean,]
1991 Cassigerinelloita amekiensis Stolk. - Huber : p.439 pl. 7; fig. 11 [lower middle Eocene, ODP Site 738, Kerguelen
Plateau, southern Indian Ocean]
1992 Cassigerinelloita amekiensis Stolk. - Li & Radford : p. 595-599 pl. 1, fig. 1-13;
pl. 2, fig. 1-9 [lower
middle Eocene, ODP Site 749, Kerguelen Plateau,
southern Indian Ocean]
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| References: |
Stolk,J.. (1965):
Contribution a l'etude des correlations microfaunique du Tertiaire inferieur de la Nigerie meridionale . Bureau Recherches Geologiques Minerales Memoire Vol. 32 p. 247-267
Stott,L.D. and Kennett,J.P. (1990):
Antarctic Paleogene planktonic foraminifer biostratigraphy: ODP Leg 113, Sites 689 and 690.
In: Proceedings of the Ocean Drilling Program Vol. 113 p. 549-569
Nocchi,M.; Amici,E. and Premoli Silva,I. (1991):
Planktonic Foraminiferal Biostratigraphy and Paleoenvironmental Interpretation of Paleocene Faunas from the Subantartic Transect, Leg 114.
In: Proceedings of the Ocean Drilling Program, Scientific Results Vol. 114 Eds: Ciesielski, P.F.Kristoffersen, Y.Al, E. p. 233-279
Huber,B.T. (1991):
Paleogene and early Neogene planktonic foraminifer biostratigraphy of Sites 738 and 744, Kerguelen Plateau (southern Indian Ocean).
In: Proceedings of the Ocean Drilling Program, Scientific Results Vol. 119 Eds: Leckie, R.M.Sigurdsson, H.Acton, G.D.Draper, G. p. 427-449
Li,Q. and Radford,S.S.. (1992):
Morphology and affinity of the planktonic foraminifer Cassigerinelloita amekiensis Stolk and reclassification of Cassigerinelloita Stolk.
In: Proceedings of the Ocean Drilling Program, Scientific Results, Ocean Drilling Program Vol. 120 Eds: Wise, J.S.W..Schlich, R..and others p. 595-602
Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006):
Atlas of Eocene Planktonic Foraminifera. p. 1-513
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