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Species Blefuscuiana speetonensis Banner & Desai 1988


Diagnosis / Definition:
Banner & Desai (1988):
The test is a low trochospire with about six chambers in the first whorl and five to seven chambers in the final whorl. The spiral side is typically wholly evolute and flat but may become slightly involute and concave with growth or with reduction of chamber number or both. The intercameral sutures of the spiral side are straight and slightly oblique and become increasingly depressed in the final whorl as the chambers become increasingly globular. The umbilicus is moderately broad (with breadth about 25% of the test diameter) and open; the intercameral sutures on the umbilical side are virtually radial. On both the spiral and umbilical sides, the initially reniform chambers are broadest toward their posterior ends, this asymmetry giving the earlier chambers a slightly "swept back" appearance, like ovoids with the narrower end to the anterior; the later chambers of the last whorl become subglobular. The aperture is a low arch, in early chambers extending from the umbilicus to the periphery of the previous whorl, but in the later chambers it may extend over the periphery to encroach slightly onto the spiral side. The aperture has a porticus throughout its length, broadest posteriorly. Relict apertures and portiei are visible in the umbilicus for about half of the last whorl. The surface of the test is smooth, not muricate, and is microperforate, with external diameters about 0.6µm. The whole surface is microperforate except for the umbilical shoulders, which may be imperforate.
Discussion / Comments:
Boudagher-Fadel et al. (1997):
Remarks: B. speetonensis has six subglobular chambers (h/L = 0.7 approx.) in the umbilicus, and a flat to concave, evolute dorsal side. The umbilicus is moderately broad (u/uh = 0.5 approx.) and open, with relict apertures and portici visible for about half of the last whorl. The aperture has a proticus, which is broadest posteriorly, and extends to the periphery of the penultimate whorl. The umbilical shoulders of the chambers of the last whorl are imperforate. The tendency towards planispirality shown by this species suggests that it may be ancestral to multi-chambered species of Blowiella recorded from stratigraphically younger horizons of the Late Aptian.
Systematics:

22
 Superfamilia Globigerinaceae
  Familia Praehedbergellidae
   Subfamilia Praehedbergellinae
    Genus Blefuscuiana
     Species Blefuscuiana speetonensis
Synonym list:
Banner & Desai (1988):
1974 Hedbergella planispira Tappan. - Longoria : 64-65 pl 23 figs 5-7, 17-18
1988 Blefuscuiana n sp. speetonensis Banner & Desai. - Banner & Desai : 166, 167 pl 7 figs 1-8
Boudagher-Fadel et al. (1997):
1974 Hedbergella planispira Tappan. - Longoria : p. 64, 65 pl. 23; fig. 5-7, 17, 18
1988 Blefuscuiana speetonensis Banner & Desai. - Banner & Desai : p.164 pl. 7; fig. 1-8
1993 Blefuscuiana speetonensis Banner & Desai. - Shahin : p.418 fig. 5-10
1997 Blefuscuiana speetonensis sensu stricto Banner & Desai. - Boudagher-Fadel et al. : p.157 pl. 8.11; fig. 4-10; Figure: 8.1
1997 Blefuscuiana speetonensis Banner & Desai. - Boudagher-Fadel et al. : pl. 4, fig. 1, 2 (in press)
References:

Longoria,J.F. (1974):
Stratigraphic, morphologic and taxonomic studies of Aptian planktonic Foraminifera . Revista Espanola de MicropaleontologķaNo extraord p. 1-107

Banner,F.T. and Desai,D. (1988):
A review and revision of the Jurassic-Early Cretaceous Globigerinina, with special reference to the Aptian assemblages of Speeton (North Yorkshire, England) . J. micropalaeontol. Vol. 7(2) p. 143-185

Shahin,A.M.. (1993):
Biostratigraphy of the subsurface Lower Cretaceous succession in the Bardawli area, northern Sinai, Egypt. . Neues Jahrbuch fir Geologie und Paläontologie, Monatshefte p. 413-433

Boudagher-Fadel,M.K.; Banner,F.T.; Whittaker,J.E. and Simmons,M.D. (1997):
Early Evolutionary History of Planktonic Foraminifera. Vol. 1

Boudagher-Fadel,M.K.; Banner,F.T.; Gorbatchik,T.N. and Simmons,M.D. (1997):
Barremian-Aptian planktonic foraminifera from the Crimea, compared to those from Tunisia and the North Sea area..
In: Micropalaeontology of the Former Soviet Union Eds: Simmons, M.D.
Anonymous: Unedited TaxonConcept data
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