IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 79 



observed in his paratypes (B.M.N.H. No. P. 41774), and are recorded in the present 

 study. Bronnimann & Brown 1956 stated that " The distinctive feature of Rugo- 

 truncana skewesae n. sp. is its very flat dorsal side. Globotruncana concavata (Brotzen) 

 is the only globotruncanid known to us to have flatter dorsal side." Apart from the 

 fact that G. concavata has a concave rather than a flat dorsal side, and that there 

 are at least twenty known Globotruncana species and subspecies with a flat dorsal 

 side, it is clear from their statement that these authors had completely overlooked 

 G. aegyptiaca and its related forms which were described at least six years before 

 their R. skewesae. Moreover, they described the last whorl in R. skewesae as having 



5 or 6 chambers, and included in its synonymy forms such as G. rosetta (Carsey) of 

 Plummer (1927) and G. area (Cushman) of Jennings (1936) which are actually 

 G. gagnebibi Tilev, thus indicating that they had also included within R. skewesae 

 forms related to G. gagnebini. However, as the holotype of R. skewesae is identical 

 with G. aegyptiaca aegyptiaca it is considered to be a junior synonym of the latter. 



Said & Kenawy (1956) described as G. aegyptiaca Nakkady, an entirely single- 

 keeled form which is apparently G. stuarti parva Gandolfi, as mentioned under the 

 latter species. 



The evolutionary history of G. aegyptiaca aegyptiaca is not clearly understood, 

 although the morphological features of the species may suggest its evolution from 

 G. ventricosa White through G. gagnebini Tilev and into G. aegyptiaca duwi Nakkady. 

 However, it is not known whether G. gagnebini appears lower in the section than 

 G. aegyptiaca aegyptiaca or not, as the two species were always confused with one 

 another. In the sections studied, both species were found to occur together from 

 the basal part of the Maestrichtian to the disconformity separating it from the 

 overlying basal Tertiary. Thus it is not excluded that the two species might have 

 evolved from two distinct but morphologically similar, forms. If so, the ancestral 

 stock of G. aegyptiaca aegyptiaca may be sought in a form other than G. ventricosa 

 White, which is more closely related to G. gagnebini Tilev. Globotruncana tricarinata 

 colombiana Gandolfi is the only known, morphologically similar Globotruncana 

 species which appears in older strata, and thus may possibly represent the ancestral 

 stock from which G. aegyptiaca aegyptiaca has evolved. 



Hypotypes. P.45512-13. 



Horizon and locality. Figured specimens from Sample No. 16, Gebel 

 Owaina section. 



Stratigraphical range : Nakkady (1950) described G. aegyptiaca aegyptiaca 

 from the Maestrichtian Esna shale of the Abu Durba section, western Sinai, Egypt, 

 and recorded it as rare to abundant in the chalk of W. Mellaha (Eastern Desert), 

 the shale of W. Danili (western Sinai), and frequent to abundant in the chalk of 

 G. Duwi (Eastern Desert), Egypt. The species was also recorded from the Camp- 

 anian-Maestrichtian of both the Qabeliat and Sudr sections, Sinai, Egypt (Nakkady 



6 Osman 1954), and as R. skewesae from the Middle Maestrichtian of the Navarro 

 group of Texas, (Bronnimann & Brown 1956). 



