[18 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



figure. Gandolfi (1955) described G. gansseri subgansseri as a new subspecies thus 

 changing the name of Bolli's form to G. gansseri gansseri. However, the form 

 figured by Gandolfi (1955) as G. gansseri gansseri Bolli was found to differ from the 

 holotype of Bolli and is thus considered here separately. 



Bronnimann & Brown (1956) introduced Rugotruncana as a new genus and 

 included G. gansseri Bolli in it. However, as mentioned above, Rugotruncana 

 Bronnimann & Brown 1956 is considered a junior synonym of Globotruncana Cush- 

 man 1927. These authors (1956) showed by thin sections of G. gansseri gansseri 

 that the early part of the test has two well-developed marginal keels in spite of the 

 entirely single-keeled last whorl. Pessagno (i960) also observed a double-keeled, 

 rugoglobigerine nepionic stage in thin sections of G. gansseri gansseri , but added that 

 some individuals may lack this initial double keel. 



Olsson (i960) described as G. monmoathensis , a form which most probably belongs 

 to the present subspecies. 



Globotruncana gansseri Bolli (1951) was found to include the following four distinct 

 subspecies : 



Globotruncana gansseri gansseri Bolli 1951. 

 Globotruncana gansseri subgansseri Gandolfi 1955. 

 Globotruncana gansseri dicarinata Pessagno i960. 

 Globotruncana gansseri gandolfii subsp. nov. 



However, because of its entirely double keel, G. gansseri dicarinata appears to 

 be morphologically distinct, despite the fact that thin sections of G. gansseri gansseri 

 showed a double-keeled nepionic stage. Further study may prove that it should 

 be treated separately although it has some features in common with the G. gansseri 

 group. 



Gandolfi (1955) suggested the evolution of G. gansseri gansseri Bolli from G. 

 rosetta pettersi Gandolfi which was said to appear in older strata and to die out 

 completely before the first appearance of G. gansseri gansseri. However, Pessagno 

 (i960) suggested the evolution of G. gansseri gansseri from G. gansseri dicarinata, 

 while the present study favours its evolution from G. rosetta rosetta (Carsey). On 

 the other hand, G. gansseri gansseri might possibly have evolved in two directions, 

 one leading to G. gansseri subgansseri and the other to G. gansseri gandolfii. 



Hypotype. P.45543. 



Horizon and locality. Figured specimen, from Sample No. 18, W. El-Shar- 

 awna section. 



Stratigraphical range. Globotruncana gansseri gansseri was first described 

 by Bolli (1951) from the Maestrichtian Lantern marl, Guayaguayare formation of 

 Trinidad and all subsequent references restricted its range to the Maestrichtian. 



In the Esna-Idfu region, G. gansseri gansseri appears in the basal part of the 

 Pecten (Chlamys) mayereymari marl (Pecten farafraensis marl) ; it floods this rock unit 

 and the basal part of the overlying shale member, characterizing a particular faunal 

 zone, the G. gansseri Zone. It continues in the Upper Sharawna shale, fading out 



