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Species Globanomalina luxorensis Nakkady 1950 | ||||||
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| Diagnosis / Definition: | ||||||
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Pearson et al. (2006): DESCRIPTION. Type of wall: Smooth, normal perforate. Test morphology: Test very low trochospiral, compressed, tightly coiled, oval in outline, slightly lobulate; chambers inflated, globular; in umbilical view normally 6-7 chambers in ultimate whorl, increasing rapidly in size, sutures moderately depressed, straight to slightly curved, umbilicus small, circular in shape; in spiral view 6-7, occasionally 5 or up to 8, chambers in ultimate whorl, increasing rapidly in size, sutures moderately depressed, straight to slightly curved, inner whorl of chambers depressed, evolute to partly involute; in edge view primary aperture an oval, umbilical-extraumbilical high arch bordered by a narrow lip which extends slightly onto the spiral side but not to the spiral suture; test compressed with a rounded periphery; peripheral margin perforate. Size: Maximum diameter of holotype 0.25 mm, thickness 0.15 mm. |
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| Discussion / Comments: | ||||||
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Pearson et al. (2006): DISTINGUISHING FEATURES.- Globanomalina luxorensis is characterized by its very low trochospiral test, globular chambers, rounded axial periphery, and an arched aperture that extends over the axial periphery to the spiral side, but not to the trace of the spiral suture. The species is regarded as representing the transitional morphology from a trochospiral to a planispiral test, but is not planispiral according to the criterion of Blow (1979, p. 1060; discussed above). DISCUSSION.- Globanomalina luxorensis has been a poorly known species since it was first described. This may, in part, be due to its limited occurrence and abundance in the stratigraphic record and, perhaps, to its having been overlooked or included in Globanomalina chapmani, Globanomalina ovalis Haque, 1956, or Pseudohastigerina wilcoxensis. Banner (1989) concluded that G. luxorensis could be separated from G. ovalis, although he earlier (Banner, 1982) had considered G. luxorensis as the senior synonym of G. ovalis. He regarded G. luxorensis as the immediate ancestor of P. wilcoxensis. Recently, Speijer and Samir (1997) noted the association of G. luxorensis with the negative ò13C excursion in the middle part of Zone P5 (of Berggren and others, 1995), which they suggested as the point for marking the boundary between the Paleocene and the Eocene in a Global Stratotype Section and Point (GSSP). However, they concluded, in contrast to Banner (1 989), that G. ovalis was a junior synonym of G. luxorensis and found that in Egypt G. luxorensis was extremely rare below the ò13C excursion. We would agree with Banner that the two species can be separated, but part of the confusion appears to be due to poor preservation (see Banner, 1989) and to lack of sufficient specimens below the 6I3C excursion. Globanomalina ovalis is common in Zone P4 in southern India (Olsson and others, 1999), which suggests that the species was common in the Indian Ocean region, and records of the species in New Zealand indicate its widespread distribution in the late Paleocene. Globanomalina ovalis usually has 5 chambers in the ultimate whorl in contrast to G. luxorensis which usually has 6-7 chambers in the ultimate whorl. Occasionally, 6-chambered forms and 5-chambered forms are found in assemblages of each species, respectively (see Speijer and Samir, pl. 2, figs. 2a-c as an example). The chambers in G. ovalis in edge view are oval in shape, and wider than high. Because of this, the chambers tend to extend over the spiral side presenting a planispiral appearance and, as Banner (1989) noted, the spiral "side becomes incompletely evolute and slightly concave in shape" (p. 177). The aperture, however, only extends extraumbilically to the medium point of the axial periphery, in contrast to G. luxorensis where the aperture extends slightly over the axial periphery but not to the trace of the spiral suture. In edge view the chambers in G. luxorensis are more globular, equidimensional, or even slightly compressed. Given these morphological criteria the morphotype recorded as ex interc G.(T.)chapmani Parr and Pseudohastigerina wilcoxensis (Cushman and Ponton) by Blow (1979, pl. lll: fig. 5) is more appropriately placed in G. luxorensis rather than in G. ovalis (as recorded by Olsson and others, 1999). PHYLOGENETlC RELATIONSHIPS.- Globanomalina luxorensis evolved from G. ovalis by an increase of number of chambers in the final whorl, development of more globular equidimensional chambers, and by the migration of the aperture slightly over the axial periphery onto the spiral side. In turn, G. luxorensis gave rise to Pseudohastigerina wileoxensis through the development of an equatorial aperture and a planispiral test. The species is the end-member of the Globanomalina imitata-G. ovalis-G. luxorensis lineage which led to the genus Pseudohastigerina. STRATIGRAPHIC RANGE.- Zone P5 to top of Zone E3. GEOGRAPHIC DISTRIBUTION.- Global in low to mid latitudes. STABLE ISOTOPE PALEOBIOL0GY.- Our data show relatively negative oxygen values that suggest a shallow habitat above the thermocline (R. K. Olsson, unpublished data). |
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| Systematics: | ||||||
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35 Ordo Foraminiferida Superfamilia Globigerinaceae Familia Hedbergellidae Genus Globanomalina Species Globanomalina luxorensis |
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| Synonym list: | ||||||
| Pearson et al. (2006): 1950 Anomalina luxorensis Nakkady. - Nakkady : p.691 pl. 90; fig. 39-41 [upper Paleocene, Esna Shale, Abu Durba, Western Sinai,
Egypt]
1950 Anomalina luxorensis Nakkady. - Nakkady : p.465 pl. 5; fig. 1a-c [upper
Paleocene, Gabal Um Elghanayem, Kharga Oasis, Western
Desert, Egypt]
p 1967 Pseudohastigerina wilcoxensis Cushman & Ponton. - Berggren et al. : p.278 text-fig. 2.d-f, m-r [lower Eocene Zone P6, Manasquan Fm.,
New Jersey]
1975 Pseudohastigerina wilcoxensis Cushman & Ponton. - Stainforth et al. : p.243 fig. 99.6a-c (reillustration of Berggren and others, 1967, text-fig.
2: p-r)
p 1979 Globorotalia (Turborotalia) chapmani Parr. - Blow : p.1059 pl. 116; fig. 1, 3-5 (not pl. 11 6: fig. 2); [lower Eocene Zone P7,
Kilwa area, Tanzania]; [Not
Parr, 1938]
1979 Globorotalia (Turborotalia) sp . - Blow : p.1061 pl. 111; fig. 5 [lower Eocene Zone P7, Moogli Mudstones, Kagua,
Papua]; [recorded as ex interc G. (T.) chapmani
and Pseudohastigerina wilcoxensis]
1990 Pseudohastigerina wilcoxensis Cushman & Ponton. - Stott & Kennett : p.560 pl. 5; fig. 5, 6 [lower Eocene Zone AP6, ODP Hole 6908, Maud Rise,
Antarctic Ocean]; [Not Cushman and Ponton, 1932]
p 1997 Globanomalina luxorensis Nakkady. - Speijer & Samir : p.53 pl. l, fig. 4a-5c [lower Eocene, 4a-c, Gebel Aweina, Egypt; 5a-c, Gebel Duwi, Egypt];
pl. 2, fig. la-4c [lower Eocene, la-c,
Pyramidal Hill, Egypt; 2a-c, Darb Daga; 3a-4c, Gebel Aweina, Egypt] (not pl. l, fig. 6a-c)
2006 Globanomalina luxorensis Nakkady. - Pearson et al. : p.417 pl. 14.1; fig. 1-10
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| Specimen: | ||||||
| Natural History Museum, London, Inventory number: P.42400 |
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| References: | ||||||
Nakkady,S.E. (1950): Berggren,W.A.; Olsson,R.K. and Reyment,R.A. (1967): Stainforth,R.M.; Lamb,J.L.; Luterbacher,H.P.; Beard,J.H. and Jeffords,R.M. (1975): Blow,W.H. (1979): Stott,L.D. and Kennett,J.P. (1990): Speijer,R.P.. and Samir,A.M.. (1997): Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006): |
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| Anonymous: Unedited TaxonConcept data | ||||||
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