Conoglobigerina balakhmatovae Morozova 1961 from: Boudagher-Fadel, M.K.Banner, F.T.Whittaker, J.E.Simmons, M.D. (1997): Early Evolutionary History of Planktonic Foraminifera. Vol. 1 . |
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Species Conoglobigerina balakhmatovae Morozova 1961 |
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Discussion / Comments: |
Boudagher-Fadel et al. (1997):
Remarks: The test is low spired and the dorsal
surface is only slightly convex. This species also
differs from C. dagestanica Morozova in having
a faster rate of chamber enlargement. In C. balakhmatovae,
the hlb = 0.7 (approx.), whereas in C.
dagestanica the hlb = 0.5 (approx.). Ventrally,
four chambers abut the umbilicus in each of these
species, but about six chambers occupy the first
whorl in C. balakhmatovae (Plate 2.4, Figs 9, 16
herein; also Morozova, 1961, plate 1, fig. 1).
Morozova (in Morozova and Moskalenko,
1961, p. 61) believed C. balakhmatovae to be
dimorphic, the microspheric generation having
five or six chambers in the first whorl, but the
megalospheric possessing only three or four chambers
per whorl initially. Her type specimens were
from Early Bathonian of Dagestan. The specimen
from the Bajocian of the north west Caucasus,
imaged in SEM by Gorbachik (1986), shows five
chambers per whorl visible initially; Morozova
(1961 op. cit.) obtained similar specimens from
the Late Bajocian of Turkrnenia. Therefore, this
generation with five to six chambers initially ranged from Late Bajocian to Early Bathonian.
The forms with three or four chambers in the
earliest whorls appear to have been rare; her illustrations
which do not clearly exhibit the number
of chambers in the early whorls may have been
interpreted as possessing few chambers per whorl,
but the whorls may have been obscured by
sediment. Certainly, there are no specimens
photographed either by Morozova (1961), or by
us (Plate 2.4) which show so few chambers in the
early whorls. In our opinion, dimorphism in this
species is not yet proven. Nevertheless, it is probable
that dimorphism did occur in some species
of Conoglobigerina, as in C. dagestanica (above). |
Systematics: |
22 Subordo Globigerinina
Superfamilia Favusellacea
Familia Conoglobigerinidae
Genus Conoglobigerina
Species Conoglobigerina balakhmatovae
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Synonym list: |
Boudagher-Fadel et al. (1997):
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References: |
Balakhmatova,V.T.. (1953): On Middle Jurassic Globigerinidae and Globorotaliidae . Sbornik v Paleontologija i Stratigrafia, Trudi Vsesojuznyi Nauchno-Issledovatelskyj Geologiczeskij-Razvedochnyj Instituta p. 86-89
Morozova,V.G. and Moskalenko,T.A.. (1961): Planktonnie foraminiferi progranichnikh otlozhenii Bayosskogo i Batskogo yarusov tsentral'nogo Dagestana (severovostochnii Kavkaz) . Voprosy Mikropaleontologii Vol. 5 p. 3-30
Brönnimann,P. and Wernli,R.. (1971): Les 'Globigerines' du Dogger du Jura méridional. In: Proceedings of the Second Planktonic Corference, Roma 1970 Vol. 1 Eds: Farinacci, A. p. 117-128
Gorbatchik,T.N. (1986): Jurassic and Early Cretaceous planktonic foraminifera of the south of the USSR [in Russian]. p. 239
Boudagher-Fadel,M.K.; Banner,F.T.; Whittaker,J.E. and Simmons,M.D. (1997): Early Evolutionary History of Planktonic Foraminifera. Vol. 1
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