Hedbergella rischi Moullade 1974 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 Hedbergella rischi Moullade 1974 |
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| Discussion / Comments: |
Bellier & Moullade (2002):
Initially fully described and illustrated, hut left in
open nomenclature under the name "Hedbergella
(Hedbergella) sp., aft. infracretacea'" (Moullade,
1966), this biostratigraphically significant middle
Albian morphotype was subsequently formerly named
(Moullade, 1974) within a short note referring to
the description of 1966. This two-step process probably
explains why Hedbergella rischi was not included
in the usual planktonic foraminiferal handbooks (Caton,
1985; BouDagher-Fadel et al., 1997), and is rarely
mentioned (Br6h6ret et al., 1986; Sigal, 1987;
Premoli Silva and Sliter, 1995).
Hedbergella rischi, typically a 5 to 6-chambered
species, evolved from the P. infracretacea-like morphogroup
in the middle Albian and differs mainly
from the latter by a slightly faster increase of the
spire height and thus size of the last chambers, and
by a slightly more open umbilicus. In the upper
Albian, some evolved 6.5 1o 7-chambered specimens
of H. rischi show progressive morphological similarities
with Ticinella primula LUTERBACHER, 1963, but
are still devoid of sutural accessory apertures. As ill
the Vocontian material (Moullade, 1966), samples
from Holes 1050C and 1052E provide all the intermediate
morphological stages between the two taxa;
this gradational evolution can be interpreted as evidence
of their phylogenetic relationship.
Hedbergella yezoana TMCa_YANAGI and IWAMOTO,
1962 (nora. transl. ; initially described from the upper
Albian of Japan as lledbergella trocoidea (GANDOLFI)
subsp, yezoana) differs from typical H. rischi by having
7 to 8 chambers, instead of 5 to 6. Morphologically
H. yezoana resembles also T. primuht but on
the basis of its initial description appears to be devoid
of accessory apertures. This species was not
identified within our material and might be endemic
to Japan. |
| Synonym list: |
Moullade et al. (2002):
Bellier & Moullade (2002):
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| References: |
Moullade,M. (1966):
Etude stratigraphique et micropaléontologique du Crétacé inférieur de la "fosse vocontienne" . Documents des Laboratoires de Géologie de la Faculté des Sciences de Lyon Vol. 15 p. 1-369
Risch,H. (1969):
Stratigraphie der höheren Unterkreide der bayerischen Kalkalpen mit Hilfe von Mikrofossilien. Dissertation. p. 180
Moullade,M. (1974):
Zones de Foraminifères du Crétacé inférieur mésogéen . Comptes Rendus de l’Académie des Sciences, Paris (Série D) Vol. 278 p. 1813–1816
Leckie,M.R. (1984):
Mid-Cretaceous planktonic foraminiferal biostratigraphy off Morocco, Deep Sea Drilling Project Leg 79, Sites 545 and 547 . Initial Reports of the Deep Sea Drilling Project Vol. 79 p. 579–620
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
Moullade,M.; Bellier,J.P. and Tronchetti,G. (2002):
Hierarchy of criteria, evolutionary processes and taxonomic simplification in the classification of Lower Cretaceous planktonic foraminifera . Cretaceous Research Vol. 23 p. 111-148
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