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Species Conoglobigerina balakhmatovae Morozova 1961


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
Synonym list:
Boudagher-Fadel et al. (1997):
1953 Globigerina sp. . - Balakhmatova : p.88 text-fig. 1a-c
p 1961 Globigerina (Eoglobigerina) balakhmatovae Morozova. - Morozova & Moskalenko : p.23 pl. 1; fig. 1-8, 12 (not fig. 9-11)
1971 "Globigerina" balakhmatovae Morozova. - Brönnimann & Wernli : p.121 pl. 1, fig. 1-4; pl. 4, fig. 1, 2
1986 Globuligerina balakhmatovae Morozova. - Gorbatchik : pl. 4; fig. 1-3
1997 Conoglobigerina balakhmatovae Morozova. - Boudagher-Fadel et al. : p.39 pl. 2.4; fig. 7-12, 16; Figure: 2.2
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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