Rotalipora globotruncanoides Sigal 1948 from: Bellier, J.P.Moullade, M. (2002): Lower Cretaceous Planktonik Foraminiferal Biostratigraphy Of The Western North Atlantic (ODP LEG 171B), And Taxonomic Clarification Of Key Index Species . Revue de Micropaleontologie Vol. 45(1) p. 9-26 . |
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Species Rotalipora globotruncanoides Sigal 1948 |
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Alternative name: |
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Discussion / Comments: |
Bellier & Moullade (2002):
Thalmanninella (type-species: T. brotzeni SIGAL,
1948) was distinguished by Sigal (1948) from
Rotalipora (type-species : R. turonica BROTZEN,
1942), on the basis of the position of the supplementary
apertures. However, it has been shown that
these apertures have the same origin and their position
changes within the evolution of the species and
through a specimen's ontogeny. Thus, there is no
need for the genus Thalmanninella. In addition, as
stated by Robaszynski and Caron (1995), R. brotzeni
SIGAL is a junior synonym of R. globotruncanoides
SIGAL, 1948.
The species concept of lower Cenomanian R. globotruncanoides
used here corresponds with the initial
description of Sigal, 1948, i.e,. 5 to 7 chambers
in the last whorl, last sutures arched and very slightly
depressed on the umbilical side.Some older (uppermost Albian) specimens (cf.
P1.2, fig. 1-3) show more straight and depressed last
umbilical sutures. They are named R. aft. R. globotruncanoides
and may correspond to the initial R.
brotzeni concept of Robaszynski, Caron and the European
Working Group on Planktonic Foraminifera
(1979), the R. aft. R. greenhornensis (=brotzeni)
concept of Moullade and Porthauh (in Moullade,
1966) and/or the species R. tehamaensis of Marianos
and Zingula (1966). The identification of this Vraconian
stratigraphic precursor within the species range
is of importance for the discussion about the Albian-
Cenomanian boundary (see bio-events section before).
On the other hand, R. globotruncanoides is distinguished
from R. gandolfii Luterbacher and Premoll
Silva, 1962 by showing strongly oblique sutures
on the spiral side, a tendency toward a more pronounced
asymmetrical test, raised umbilical sutures,
and well-developed umbilical supplementary apertures.
At the R. reicheli / R. cushmani zonal boundary,
R. globotruncanoides gave rise to R. greenhornensis
(Morrow, 1934), which differs from R.
globotruncanoides mainly by a higher (8-10) number
of chambers in the last whorl; the chambers of the
last whorl are elongated and dorsally crescent-shaped;
the sutures are strongly curved and raised on
both the spiral and umbilical side. Our observations
in Hole 1050C show that the LOs of Rotalipora
greenhornensis and R. globotruncanoides coincide
with that of R. cushmani (Morrow, 1934). |
Synonym list: |
Bellier & Moullade (2002):
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Was used in synonym list of: |
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References: |
Sigal,J. (1948): Notes sur les genres de foraminiferes Rotalipora Brotzen 1942 et Thalmanninella; famille des Globorotaliidae . Revue de l'Institut Francais du Petrole Vol. 3(4) p. 95-103
Robaszynski,F.; Caron,M.; Amedro,F..; Dupuis,C..; Hardenbol,J.; Gonzalez Donoso,J.M..; Linares,D.. and Gartner,S. (1993): Le Cénomanien de la région de Kalaat Senan (Tunisie centrale) : Litho-biostratigraphie et interprétation séquentielle. . Rev. Paléobiol. Vol. 12 p. 351-505
Bellier,J.P. and Moullade,M. (2002): Lower Cretaceous Planktonik Foraminiferal Biostratigraphy Of The Western North Atlantic (ODP LEG 171B), And Taxonomic Clarification Of Key Index Species . Revue de Micropaleontologie Vol. 45(1) p. 9-26
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