Sphenolithus disbelemnos
Set number: 899
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Set number: 900
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Set number: 898
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Set number: 897
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Set number: 896
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Set number: 895
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Set number: 894
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Set number: 893
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Set number: 870
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Set number: 891
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Set number: 869
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Set number: 868
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Set number: 274
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together with Sphenolithus disbelemnos
Set number: 881
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Sphenolithus disbelemnos Fornaciari & Rio, 1996
Sphenolithus aubryae de Kaenel & Villa, 1996
Small (3.0-5.0µm), elongated species of Sphenolithus Deflandre in Grassé, 1952 having a diminutive clustered apical cycle resembles a bouquet of flower at 45° [its segments radiating outward distally]. The apical cycle has maximum birefringence at 45° but extinct (dim) at 0°.
The height of the elongated proximal cycle with a very shallow concave base is always distinctly greater than the height of the lateral cycle. The segments of the proximal cycle aligned longitudinally.
The cylindrical proximal cycle has irregular quadrilateral shape segments in the axial section. The inner ends of these segments are joined most of their second-longest side along the longitudinal axis, thus creating a very shallow conical proximal depression.
Sphenolithus disbelemnos differs from Sphenolithus dissimilis Bukry and Percival, 1971 by its distinctly greater height of the proximal cycle than the lateral cycle. In Sphenolithus dissimilis, the heights of the proximal cycle and apical cycle are about the same.
Sphenolithus disbelemnos is distinguished from Sphenolithus quasibelemnos Varol, in prep. by having a bouquet shape clustered apical cycle instead of a biconical apical spine. Moreover, Sphenolithus disbelemnos has a cylindrical proximal cycle, whereas Sphenolithus quasibelemnos has a frustum shape proximal cycle.
Bergen, J. A., de Kaenel, E., Blair, S. A., Boesiger, T. M., Browning, E., 2017. Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research 37(2-3), 77-112.
Bukry, D., Percival, S. F., 1971. New Tertiary calcareous nannofossils. Tulane Studies in Geology and Paleontology 8, 123-146.
Deflandre, G., 1952. Classe des Coccolithophoridés. (Coccolithophoridae. Lohmann, 1902). In: Grassé, P. P. (ed.), Traité de Zoologie. Masson, Paris 439-470.
de Kaenel, E., Villa, G., 1996. Oligocene-Miocene calcareous nannofossil biostratigraphy and paleoeecology from the Iberian Abyssal Plain. Proceedings of the Ocean Drilling Program, Scientific Results 149, 79-145.
Fornaciari, E., Rio, D., 1996. Latest Oligocene to early Middle Miocene quantitative calcareous nannofossil biostratigraphy in the Mediterranean region. Micropaleontology 42(1), 1-37
Holotype
Sphenolithus disbelemnos
Fornaciari & Rio, 1996
Early Miocene
ODP Leg 115, Site 709C, Western Equatorial Indian Ocean