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Subspecies Globorotalia (Turborotalia) acostaensis pseudopima Blow 1969 | ||||||
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| Diagnosis / Definition: | ||||||
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Blow (1969): Description of holotype: The large test consists of io chambers arranged in a low trochospire with 4 inflated, subspherical chambers in the final whorl (onlY 4 chambers visible ventrally). The chambers are closely appressed; the ventral intercameral sutures are not deeply incised but are shallow. The umbilicus is small, almost closed and the ventral shoulder of the final chamber overhangs the umbilicus. The aperture is interiomarginal, umbilical extraumbilical and extends slightly beyond the mid plane of the periphery and thus encroaches slightly onto the dorsal side. The aperture is a low arch and is bordered by a thickened rim like lip which is "tucked" under the inflated apertural face of the final chamber. The spire is strongly depressed and does not protrude above the plane of the dorsal surfaces of the last whorl of chambers. The ventral intercameral sutures are subradial and the dorsal spiral suture is indistinct. The wall is calcareous, radial hyaline [62a], moderately densely perforate and the pores open into comparatively small but deep pits. The early parts of the test tend to be rather rugose but the final chamber is relatively smooth without distinct hispidity. Maximum diameter of holotype 0.56 mm. |
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| Discussion / Comments: | ||||||
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Blow (1969): Remarks: This taxon develops from G. (T.) acostaensis acostaensis by reduction of the number of chambers in the last whorl, almost complete loss of the apertural lip and the acquisition of more inflated chambers. As in G. (T.) acostaensis humerosa there is a tendency for the aperture to approach a hastigerine condition but a truly symmetrical equatorial aperture has not been seen in G. (T.) acostaensis pseudopima. G. (T.) acostaensis pseudopima greatly resembles G. (T.) opima opima and virtually completely homeomorphs this form. However, G. (T.) opima opima occurs in the middle to later parts of the Oligocene whilst G. (T.) acostaensis pseudopima occurs from the Pliocene to Recent. Gross morphological distinction between the two taxa is difficult to formulate in words but subtle differences of wall texture (and ?structure) are present which may be seen in a comparison of the figures given on Pl. 35, figures 1 7, and Pl. 39, figureS 2, 3. The evolution of pseudopima is clearly displayed in the Pliocene and, thus, the taxon is stratigraphically isolated from G. (T.) opima opima. The homeomorphy between pseudopima and opima (s.s.) parallels the homeomorphy seen between G. (T.) centralis and G. (T.) inflata (see BANNER and BLOW, 1967). In these cases intra specific variation may be as great or even greater than the interspecific variation; it is this intra specific variation which makes differential diagnosis difficult to formulate even though the two taxa concerned are most distinctive within the assemblages in which they occur. Stratigraphical Range: G. (T.) acostaensis pseudopima first appears from the base of Zone N.20 (middle Pliocene) and ranges to the Recent. The holotype was obtained from sample Ba.14, Sarmi formation, Otim River section, West Irian; Zone N.21. |
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| Blow (1969): 1969 Globorotalia (Turborotalia) acostaensis pseudopima Blow. - Blow : p.387 pl. 35, figs. 1-7
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| Was used in synonym list of: | ||||||
| References: | ||||||
Blow,W.H. (1969): |
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| Anonymous: Unedited TaxonConcept data | ||||||
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