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Species Morozovella variospira Belford 1984 | ||||||
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| Diagnosis / Definition: | ||||||
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Van Eijden & Smit (1991): Description. Umbilical side: Aperture extraumbilical-umbilical, a medium to high arc, on the last to the last three chambers bordered by an umbilical tooth or wide lip. Umbilicus wide and deep, usually partially covered by an umbilical tooth or teeth (Fig. 26 and PI. 5, Figs. 1 and 3). Sutures straight and deeply depressed. Four to five chambers in the final whorl (usually four and a half). Chambers increasing abruptly in size as added, but the final two or three chambers can be of subequal size (cf PI. 5, Figs. 1 with 2). Some of the final chamber(s) can be displaced toward the umbilicus. Spiral side: Outline strongly lobate. Sutures straight, with some slightly curved backward, and deeply depressed. Chambers strongly inflated. Twelve to 15 chambers, arranged in three to three and a half whorls (Fig. 26 and PI. 5, Figs. 6 and 7). Lateral view: Trochospire is usually low, sometimes moderately high in specimens with chambers displaced toward the umbilicus. Profile broadly rounded (Fig. 26 and PI. 5, Figs. 4 and 5). Wall calcareous, densely perforate surface with small pustules that grade into a honeycomb pattern. Diameter of full-grown specimens up to 0.80 mm, and usually between 0.4 and 0.7 mm. Intraspecies variability. Smaller, immature specimens with only four chambers in the final whorl may have a broad lip over the aperture of the final chamber only. The umbilicus of these specimens is narrower. Large, mature specimens may have five chambers in the final whorl, which increase gradually in size, with a number of chambers of subequal size. These specimens usually show prominent apertural teeth and a wide umbilicus. In spiral view, the stage with four rapidly enlarging chambers per whorl is easily discerned. The apertural tooth of displaced chambers is commonly weakly developed. Diagnosis. M. variospira differs from all other Paleocene species of planktonic foraminifers by the presence of apertural teeth. This, together with its large size, makes it very conspicuous and easily recognized. Small, immature specimens resemble M. pseudobulloides (Plummer, 1926), which they differ from by their larger size, wider umbilicus, and the presence of an apertural lip or tooth on at least one chamber. The only species morphologically similar are Globoquadrina altispira globosa Bolli, 1957a and Neogloboquadrina dutertrei (d'Orbigny, 1839), which have radically different stratigraphical ranges and are phylogenetically unrelated. Phylogeny. Intermediate forms between this species and M. pseudobulloides in the lower part of the range of M. variospira show that it descended from M. pseudobulloides. It may represent a gerontic form of that species. Stratigraphic distribution. Lower part of Zone P3a (M. angulata Zone) to halfway Zone P4 (P'. pseudomenardii Zone). At Site 758 it occurs in Samples 121-758A-30X-1, 115-120 cm, to 121-758A-31X-3, 115-120 cm. The species is not as variable in coiling mode as Belford (1984) thought it was, and almost all specimens are very low trochospiral. The most important difference with the original description is that prominent apertural teeth are present, which were not observed by Belford. Its Phylogenetic position and stratigraphic range are now known in some detail. |
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| Discussion / Comments: | ||||||
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Van Eijden & Smit (1991): Remarks. The figured specimens will be deposited in the Dutch National Museum of Natural History in Leiden, under the first author's name. |
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| Systematics: | ||||||
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32 Familia Globorotaliidae Genus Morozovella Species Morozovella variospira |
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| Synonym list: | ||||||
| Van Eijden & Smit (1991): 1984 Globorotalia (Turborotalia) variospira Belford. - Belford : p.18 pl. 24, figs. 15-17; pl. 25, figs. 1-7
1991 Morozovella variospira Belford. - Van Eijden & Smit : 113, 123 fig. 26; pl. 5, figs. 1-8 em.
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| Was used in synonym list of: | ||||||
| References: | ||||||
Belford,D.J. (1984): Van Eijden,A.J.M. and Smit,J. (1991): |
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| Anonymous: Unedited TaxonConcept data | ||||||
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