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Species Globorotalia (Globorotalia) paralenguaensis Blow 1969 | ||||||
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| Diagnosis / Definition: | ||||||
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Kennett & Srinivasan (1983): Test low trochospiral, the spire opens slowly, later more rapidly; equatorial profile ovate, very slightly lobulate; axial profile unequally biconvex, with more vaulted ventral side; peripheral margin with a distinct imperforate carina, chambers six to eight in the final whorl, less tightly coiled; spiral sutures on early chambers strongly curved, later more nearly radial, depressed; on umbilical side almost radial, depressed; surface smooth, densely perforate; umbilicus closed; aperture interiomarginal, umbilical-extraumbilical, a low arch bordered by a lip. Blow (1969): Description of holotype: Test small, coiled in a low trochospire with about 15 16 chambers comprising the spire and with 6 chambers in the final whorl. The spire opens slowly at first then shows a more rapidly opening coiling mode with a distinct flare for the later parts of the last convolution at least; the chambers are tightly coiled in the early part of the test but become much less tightly coiled later. The equatorial profile is non lobulate becoming very slightly lobulate over the periphery of the last two or three chambers. The axial profile shows an unequally biconvex test with the dorsal surface slightly vaulted and the ventral surface rather more distinctly vaulted. The peripheral margin bears a distinct "imperforate" carina but the dorsal intercameral sutures are not limbate. Dorsal intercameral sutures only very slightly incised and show step like features for the last two or three chambers. The earlier dorsal intercameral sutures are strongly recurved but the later dorsal intercameral sutures become more nearly radially disposed with some peripheral retortion. In dorsal aspect the earlier chambers are almost hemi circular in shape but the final two or three chambers are more quadrate or rectangular in overall shape. The ventral intercameral sutures are radial to slightly sinuous, moderately incised between the somewhat inflated ventral surfaces of the chambers. The umbilicus is completely closed. The aperture is interiomarginal, umbilical extraumbilical but is laterally restricted and is bordered by a distinct rim like lip; the aperture is a moderately arched opening. The wall is calcareous, radial hyaline [62a], translucent with only very small scattered pustules confined to the area in the vicinity of the aperture. The wall is very finely perforate but the pores are comparatively widely spaced and do not open into distinct pore pits. Maximum diameter of holotype 0.25 mm. |
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| Discussion / Comments: | ||||||
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Kennett & Srinivasan (1983): Gr. (Gr.) paralenguaensis is intermediate between Gr. (Gr.) lenguaensis Bolli and Gr. (Gr.) merotumida Blow and Banner. The former has a more circular equatorial profile and a tightly coiled test; the latter differs in possessing a distinct keel. Blow (1969): Remarks: G. (G.) paralenguaensis, combines many of the morphological features seen in G. (T.) lenguaensis and G. (G.) merotumida and the taxon appears to be a morphogenetic link between the two forms. Thus G, (G.) paralenguaensis, displays, in the earlier stages of ontogeny, the chamber shape, arrangement and coiling mode seen in G. (T.) lenguaensis. On the other hand, the later stages in the ontogeny of G. (G.) paralenguaensis, display the morphological features of chamber shape, presence of a carina, apertural characteristics and later coiling mode similar to those of G. (G.) merotumida. Thus, the earlier stages of G. (G.) paralenguaensis, show the similar strongly recurved dorsal intercameral sutures as seen throughout the whole of the test of G. (T.) lenguaensis. The spire in G. (T.) lenguaensis opens slowly and regularly and the chambers are similar in shape for all stages of ontogeny but in paralenguaensis the early "lenguaensis like" morphology is followed by the spire suddenly opening more rapidly and the chambers adopting the dorsal shape as seen in G. (G.) merotumida. G. (G.) paralenguaensis retains the ventral characteristics of G. (T.) lenguaensis in possessing a completely closed umbilicus but possesses a true "imperforate" carina which is characteristic of the descendant form G. (G.) merotumida. Both the holotype and the figured paratype are completely carinate but the paratype also possesses limbate dorsal intercameral sutures (Pl. 46, figure 2) which are not seen in the holotype. It is likely that the paratype should be considered as a little more phylogenetically advanced than the holotype. Stratigraphical Range: G. (G.) paralenguaensis has a short range in the later parts of Zone N.15 and the earlier parts of Zone N.16. The holotype was obtained from sample CS.222, Kariava Hadina Creek Traverse, Papua; basal Zone N.16. |
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| Kennett & Srinivasan (1983): 1969 Globorotalia (Globorotalia) paralenguaensis Blow. - Blow : p.402 pl 46 figs 1-6
Blow (1969): 1969 Globorotalia (Globorotalia) paralenguaensis Blow. - Blow : p.402 pl. 46, figs. 1-6
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| References: | ||||||
Blow,W.H. (1969): Kennett,J. and Srinivasan,M.S. (1983): |
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| Anonymous: Unedited TaxonConcept data | ||||||
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