Missed and rare species

The following discussion is based on plots of physical parameters versus relative abundances of species. Optima, suboptima, and ranges for these parameters are listed in numeric form in the appendix for each species. The sequence of species presented in this section follows Hemleben et al. (1989). Globorotalia ungulata Bermudez, 1960 and Globorotalia cavernula Bé, 1967 were not recorded. Globorotalia theyeri Fleisher, 1974 was not recorded in the North Atlantic (Kipp, 1976) and presented taxonomic problems in the Indian Ocean. Béand Hutson (1977) used a category "G. crotonensis and G. theyeri" which occurred with relative abundances of up to 5% in sediments of the mid-latitude Indian Ocean and along the western Indian Ocean margin. Globigerinita minuta (Natland, 1938), Gallitellia vivans (Cushman, 1934), Orcadia riedeli (Roegl and Bolli, 1973), Streptochilus globigerus (Schwager, 1866), Tenuitella parkerae (Broennimann and Resig, 1972), and Turborotalita clarkei (Roegl and Bolli, 1973) were not observed due to their small size. Tenuitella fleisheri Li, 1987 was described after CLIMAP (1976, 1981) and was not observed due to its small size (<150 micrometers).

Single specimens of the following species were found in one or two out of 461 samples (Fig. 5): Bergrenia pumilio (Parker, 1962), Globigerinella adamsi (Banner and Blow, 1959), Globigerinita uvula (Ehrenberg, 1861) = G. bradyi Wiesner, 1931, Tenuitella iota (Parker, 1962), and Hastigerina digitata (Rhumbler, 1911). Bergrenia pumilio and G. adamsi (Indo-Pacific species) occurred in the tropical Indian Ocean, G. uvula in the equatorial Atlantic (considered to be a high latitude species by Hemleben et al., 1989), T. iota in the subtropical and temperate Indian Ocean, and H. digitata in the southern tropical Indian Ocean. H. digitata has a very low preservation potential. The other species, except B. Pumilio and G. adamsi, may have been missed in most samples due to their small size.

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Figure 5: Relative abundances of species observed in only few samples plotted vs. latitude. See text for discussion.

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