VOL. 29, N 1, 2010

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1 VOL. 29, N 1, 2010

2 Revue de Paléobiologie, Genève (juin 2010) 29 (1) : ISSN Nummulites crassichordatus n.sp. (N. laevigatus group, Foraminifera) from the Middle Eocene of the Citadel section, Gebel Mokattam, Egypt Mohamed Boukhary 1, Aly I. Hussein 2 & Yasmine Hussein-Kamel 3 Abstract The Middle Eocene larger foraminifera of the Mokattam Formation corpping out at the Citadel section, north of Gebel Mokattam, were studied. The Mokattam Formation has yielded Nummulites crassichordatus n. sp. kwhich belongs to the Nummulites laevigatus group. In addition Nummulites lyelli morphotype 1 and Nummulites lyelli morphotype 2 are nominated according to the nature of septa and also described and both belong to Nummulites lyelli subgroup, Boukhary & Kamal, These morphotypes : Nummulites lyelli morphotype 1 is comparable with Nummulites gizehensis, ontogeny of which grades from lax to tight (like that of Nummulites gizehensis). Also Nummulites lyelli morphotype 2 is comparable with Nummulites lyelli s.str., that its ontogeny grades from tight to lax (like that of Nummulites lyelli). These two morphotypes 1&2 exist at the bottom and the top of Nummulites praelyelli bank Key words Nummulites, Middle Eocene, Stratigraphy, Systematic Paleontology, Gebel Mokattam, Egypt. I. INTRODUCTION The Middle Eocene larger foraminiferal Nummulites faunas are important rock forming elements in most of the Paleogene sediments of Egypt particularly the sedimentary sequences cropping out in the Greater Cairo area. These Nummulites has attracted the attention of many authors (e.g. De La Harpe, ; Said 1951 ; Cuvillier, 1930 ; Blondeau, 1972 ; Boukhary, 1988 ; Boukhary & Hussein-Kamel, 1993 ; Boukhary & Kamal, 2003 ; Hussein, 2003 ; Hussein et al., 2004). The present study is based on samples collected from Middle Eocene nummulitic rocks of the sequence cropping out and underlying the Citadel of Salah El Din north of Gebel Mokattam, East of Cairo (Fig. 1). The interval from which the Nummulites were collected is of Late Lutetian. Nummulites lyelli morphotypes 1 & 2 are transitional Fig. 1 : Stratigraphic succession of the Citadel of Salah El Din. 1 Corresponding Author : Department of Geology, Faculty of Science, Ain Shams University, Cairo, 11566, Egypt ; moboukhary@yahoo.com 2 Alyimhussein@yahoo.com 3 marmar_3303@hotmail.com

3 186 M. Boukhary, A. I. Hussein & Y. Hussein-Kamel stages that s why they are in open nomenclature, yet they are useful locally in determining the local stratigraphic range start from top Middle Lutetian to Late Lutetian according the fossil association (N. praelyelli) and facies under study. These N. praelyelli and the morphotypes had been evolved from the precursors in the east of the Nile Valley. N. crassichordatus n. sp. belongs to N. laevigatus group and in this text it is compared with N. laevigatus (Bruguiere, 1789) s.str., N. praelorioli Herb & Schaub, 1963 and N. issawii Boukhary, Hussein & Kamal, The aim of the present work is to describe the Nummulites species : N. crassichordatus n.sp. and Nummulites morphotype 1 and Nummulites morphotype 2 from the Citadel section. II. GEOLOGICAL SETTING The Eocene succession of the Gebel Mokattam is subdivided into a lower carbonate and an upper marly limestone and clastic nature units and both are distinguished on the basis of their major changes, mainly larger foraminifera. The lower carbonate unit (Mokattam Formation of Said & Martin, 1964) is characterized by the presence of Nummulites group. The upper mixed clastic-carbonate unit (Maadi Formation of Said & Martin, 1964) is mainly distinguished by a few species of larger foraminifera (Table 1). One of the classical sections in Gebel Mokattam is the section which underlies the Citadel of Salah El Din where several Nummulites banks are exposed. This section is the oldest stratigraphic sequence in Gebel Mokattam which is related to the Mokattam Formation. This unit (Mokattam Formation) consists of about 33 meters of grey to white limestones and it was given a Late Lutetian age by Boukhary & Kamal (2003) based on the presence of N. praelyelli, the direct ancestor of Nummulites lyelli. Depository The studied material is deposited among the collection of Boukhary at the Geology Department, Faculty of Science, Ain Shams University, Cairo, Egypt. III. SYSTEMATIC PALEONTOLOGY Family : Nummulitidae de Blainville, 1982 Genus : Nummulites Lamarck 1801 Type species : Nummulites laevigatus (Bruguiere, 1792) Nummulites crassichordatus n.sp. Pl. I, figs Etymology : From the thickened marginal cord which is a characteristic feature of the species Holotype : Pl. 1, fig. 10, megalospheric form, sample no. 2, Mokattam Formation, Citadel section, Gebel Mokattam, Greater Cairo area. Paratypes : 20 microspheric and 50 megalospheric specimens Locus Typicus : Citadel section, Gebel Mokattam, Greater Cairo (Fig. 1). Stratum Typicum : Fig. 1, sample 1, Citadel section, Gebel Mokattam, Greater Cairo. Microspheric (B-form) : The test is flat to discoid with a slightly inflation at the center, outer edge has a slight irregularity. Septal filaments are sinuous towards the center ; they meet Table 1 : The stratigraphic sequence of Mokattam area and the Citadel area. Salah El Din Citadel and Mokattam area (Present study) Mokattam area & Pyramids Plateau (Said & Martin, 1964, with modifications) Formation Formation Age Upper mixed clastic-carbonate unit Maadi (Middle to Late Eocene with a Late Bartonian to Early Priabonian lacuna between them) (Middle to Late Eocene) Marly limestones, bryozoans with N. decrouezae and N. praestriatus Giushi Member (Bartonian) - El Basatin section Middle Bartonian Hard Limestones with N. farisi, N. praestriatus and brachiopod species Terebratulina tenuistriata (Leymerie) N. praelyelli Member (ex Gizehensis Member) With N. discorbinus Upper Building Stone Member (Bartonian) - El Basatin section N. praelyelli Member (Late Lutetian) - Citadel section - Lower Building Stone Member (Late Lutetian) Early Bartonian Late Lutetian

4 Nummulites crassichordatus n.sp. from the Middle Eocene of the Citadel section, Egypt 187 at the outer edge with a curvature. Granulation occurs between the septal filaments, very dense on the surface, follow the septal pattern and form a concentric circle with accumulation of some granules at the center in the form of a boss. The granules are partially coalescent near the periphery. Diameter ranges from 10.5 to 17.5 mm and thickness ranges from 2.8 to 3.85 mm. Equatorial section : Spire is from lax to tight. Marginal cord is thick. Septa are arched from the base and continue higher up. Chambers are higher than long in the early whorls becoming longer than high in the last whorls. Number of whorls per radius is as follows : 12 whorls in a radius of 5.6 mm, 13 whorls in a radius of 6.2 mm and 15 whorls in a radius of 9.82 mm (Fig. 2). Megalospheric (A-form) : Test is lenticular with a swelling center. Septal filaments are sinuous at the center, radial in the middle portion of the test, with a slight wrinkle at the outer and it meets the outer periphery with a curvature. Granulation occurs all over the surface of the test, following the spiral patterns in the form of concentric circles occurring on and between the septal filaments, while in the middle portion, a large granules appear. Diameter of the test ranges from 2.8 to 3.7 mm, thickness ranges from 1.54 to 1.89 mm. Equatorial section : Spire as in B-form, cord is thick, septa in the early whorls are inclined from the base becoming more or less slightly inclined at the upper part. Chambers are quadrate in the early whorls, becoming higher than long in the last whorls. Thus the rate of the growth in the height of chambers of the last whorls is higher than that in the length of chamber. Number of whorls per radius is as follows : 3 whorls in a radius of 1.26 mm and 4 whorls in a radius of 1.75 mm (Fig. 2). Protoconch diameter ranges from 0.28 to 0.56 mm. Remarks : Nummulites crassichordatus n.sp. is typical member of N. laevigatus group due to the granulation pattern and the coalescence of the granules. Although Nummulites crassichordatus and N. somaliensis are overlapped in the measurable dimensions of the megalospheric generation, N. crassichordatus n.sp. Fig. 2 : Growth diagram of N. crassichordatus n.sp.

5 188 M. Boukhary, A. I. Hussein & Y. Hussein-Kamel differs from N. somaliensis being much smaller and much tighter than those of N. somaliensis Nuttall & Brighton, N. crassichordatus differs from N. laevigatus by having a smaller A-form of the new species. The A- and B-form of the new species have tighter spiral in a definite radius than that of N. laevigatus s.str. (12 whorls versus 5-6 mm in the new species, while that, 9-10 whorls versus 5 mm in N. laevigatus, Table 2). Although there is also a close similarity between N. crassichordatus and N. praelorioli regarding the exterior and some features of the equatorial plane, the authors do not think that their new species be assigned to N. praelorioli. The main differences is in the inclination of the septa which, particularly in the megalospheric generation, is much stronger in N. praelorioli than in N. crassichordatus. There is quite a bit of variation in the microspheric generation and some specimens are quite close to N. praelorioli. As a whole, however they are sufficiently different from N. praelorioli and in our opinion N. crassichordatus belongs to a different species as may easily seen in the camera Lucida drawing (Fig. 5) which was made by Professor Rene Herb and according to him, (written communication), it is possible that we are dealing with a new species which is named here as N. crassichordatus. Occurrence and stratigraphic distribution : Nummulites crassichordatus n.sp. is retained from samples 1 & 2 of the Mokattam Formation, Citadel section. Age : Late Lutetian. Nummulites lyelli morphotype 1 Pl. II, figs Microspheric (B-Form) : Test lenticular, thick in enter, regular margin. Granulation on the septal filaments and between them in juvenile tests, but scarce, rather peripheral in adults. The septal filaments are meandrine. Diameter (D) ranges from 20.1 mm to 29.8 mm Thickness (T) ranges from 3 mm to 6.5 mm. The diameter/ thickness relationship of N. praelyelli, N. lyelli morphotype 1 and N. lyelli morphotype 2 is shown on Fig. 4. Equatorial section : The steps of coiling are lax to tight. The cord is thick. Septa erect at the base and becoming arched in center, sometimes wrinkled. The chambers are higher than long in first whorls and become quadrate in last whorls. Fig. 3 : Growth diagram of N. lyelli morphotype 1 and N. lyelli morphotype 2.

6 Nummulites crassichordatus n.sp. from the Middle Eocene of the Citadel section, Egypt 189 Table 2 : A comparison between Nummulites crassichordatus n.sp., N. issawii Boukhary, Hussein & Kamal, 2003, N. bartovigatus Boukhary & Hussein, 2002 and N. laevigatus (Bruguiere, 1789). Megalospheric form (A-form) Characters Diameter Thickness N. somaliensis Nuttall & Brighton, 1931 D=average 3.7 mm, maximum= 4.2 mm T= average 1.5 mm, maximum= 1.8 mm N. issawii Boukhary, Hussein & Kamal, 2003 D= mm T= mm Granulation Strong circular pillars Coarse, dense on the septal filaments and center Steps of coiling No. of whorls per radius in mm Regular : laminae increasing in thickness outwards 4 whorls v. 1.8 mm 2 whorls v mm, 3 whorls v mm, 5 whorls v 2.2 mm N. bartotvigatus Boukhary & Hussein, 2002 D= mm T= mm Present N. laevigatus (Bruguiere, 1789) after Schaub, 1981) D mm T= mm Coarse at the center as in B-form Nummulites crassichordatus n.sp. Present study D= mm T= mm Following the spiral pattern in the form of concentric circles on and between the septal filaments Lax to tight Lax to tight Regular spire Lax to tight 3 whorls v 1.15 mm 4 whorls v 1.3 mm 3 whorls v 2.0 mm 5 whorls v 2.6 mm 3 whorls v 1.2 mm 4 whorls v mm Protoconch Average 0.5 mm mm mm mm mm Microspheric form (B-form) Diameter Thickness Granulation D=average 2.3 mm, maximum= 28.5 mm T= mm, average= 2.5 mm Pillars being occasionally visible D= mm T= mm Scattered randomly between and on the septal filaments reticulation D= mm T= mm D= mm T= mm D= 10.5=17.5 mm T= mm Present Polygonal Scattered between the septal filaments, very dense and granules are coalescent near the periphery Steps of coiling Irregular Lax to tight Lax to tight Regular spire Lax to tight No. of whorls per radius in mm whorls v mm 13 whorls v mm, 14 whorls v 5-6mm, 15 whorls v mm 12 whorls v 5.5 mm 13 whorls v 6.0 mm 14 whorls v 6.5 mm 15 whorls v 7.5 mm 8 whorls v 3.0 mm 9-10 whorls v 5.0 mm 15 whorls v mm 12 whorls v 5-6 mm 13 whorls v 6.3 mm 15 whorls v 9.82 mm Age Middle Eocene Bartonian Bartonian Early Lutetian Late Lutetian

7 190 M. Boukhary, A. I. Hussein & Y. Hussein-Kamel Fig. 4 : Diameter/ Thickness relationship of N. praelyelli N. lyelli morphotype 1 and N. lyelli morphotype 2. Number of whorls per radius are as follows : 24 whorls in a radius of 10.1 mm to 11.2 mm, 26 whorls in a radius of 10.3 mm to 11.0 mm, 30 whorls in a radius of 13.8 mm to 14.5 mm and 33 whorls in a radius of 14 mm (Fig. 3). Megalospheric (A-Form) : Test lenticular, margin regularly circular. Granulation on the septal filaments and scattered allover the surface in small tests, but lacking in large tests. Septal filaments sinuous (S-shaped). Diameter ranges from 3.1 mm to 6.5 mm. Thickness (T) ranges from 1.4 mm to 2 mm. Equatorial section : The spire is lax to tight. The septa are straight at the base and become higher up o wrinkled and arched in center. Chambers higher than long and become quadrate in last whorls. The number of whorls per radius are as follows : 3 whorls in a radius of 1.8 mm to 2.2 mm, 4 whorls in a radius of 2.1 mm to 2.3 mm, 5 whorls in a radius of 2.5 mm to 2.6 mm and 6 whorls in a radius of 3.0 mm (Fig. 3). The protoconch diameter ranges from 0.6 mm to 1.0 mm. Remarks : Nummulites lyelli morphotype 1 is related to N. lyelli subgroup based on the shape of septa. This is one of morphotypes which is considered as a transitional stage that give the readings of spiral diagram and the nature of septa resembles that of N. lyelli but its ontogeny contradicts this fact and resembles that of N. gizehensis s.str. (it grades from lax to tight). Plate I (Bar scale equals one mm) Figs : Nummulites crassichordatus n.sp., sample no. 2, Mokattam Formation, Late Lutetian, Citadel section Figs. 1-5 : Microspheric form, fig. 1 external view, figs. 2-3 equatorial section, figs. 4-5 axial section Figs : Megalospheric form, figs. 6-8 : external view, figs equatorial section.

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9 192 M. Boukhary, A. I. Hussein & Y. Hussein-Kamel Fig. 5 : Diagrammatic sketch of Nummulites crassichordatus n.sp. from the Citadel section, Gebel Mokattam, Greater Cairo, Egypt. Occurrence and stratigraphic distribution : This Nummulites morphotype 1 is retained from samples 3, Mokattam Formation, from Citadel section. The ontogeny of this morphotype is from lax to tight. Age : Late Lutetian. Nummulites lyelli morphotype 2 Pl. III, figs Microspheric (B-Form) : Test discoid, thickened in the center, margin rounded, thin in juvenile. Septal filaments meandrine ; granules are scattered on the septal filaments near the periphery. Diameter (D) of the test ranges from 21.2 mm to 29.1 mm ; thickness (T) of the test ranges from 2.5 mm to 5.3 mm. The diameter/ thickness relationship of N. praelyelli, N. lyelli morphotype 1 and N. lyelli morphotype 2 is shown on Fig. 4. Equatorial section : Cord is regular, thick, steps of coiling tight to lax. The septa are erect at the base and become more arched in the tight portions. Chambers are quadrate, but less in the tight whorls. The number of whorls per radius are 25 whorls in a radius of 8.1 mm, 26 whorls in a radius of 8.8 mm, 29 whorls in a radius of mm, 30 whorls in a radius of 10.4 mm, 37 whorls in a radius of 14.5 mm and 38 whorls in a radius of mm. Megalospheric (A-Form) : Test center lenticular in juveniles, flattened in adults. Granulation dense on the center of small tests and scattered allover the test and between the septal filaments in large tests. Septal filaments are sinuous towards Plate II (Bar scale equals one mm) Figs : Nummulites morphotype1, sample no. 3, Mokattam Formation, Late Lutetian, Citadel section. Figs. 1-4 : Microspheric form, figs. 1-3 equatorial sections, fig. 4 axial section. Figs : Megalospheric form, figs external view, figs equatorial section, fig. 19 axial section.

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11 194 M. Boukhary, A. I. Hussein & Y. Hussein-Kamel Table 3 : A comparison between N. lyelli morphotype 1, N. lyelli morphotype 2 and N. lyelli Archiac & Haime (1853). Megalospheric Form (A-Form) Characters Diameter Thickness Granulation Nummulites morphotype 1 (Present work) D= mm T= mm Non granulate on the large tests Nummulites morphotype 2 (Present work) D= mm T= mm Between the septal filaments in large test Nummulites lyelli Archiac & Haime, 1853 (after Boukhary & Kamal, 2003) D= mm T= mm Rare on the large tests sometimes non granulate Steps of coiling Lax to tight Tight to lax Tight to lax Number of whorls/radius 3 whorls mm 4 whorls mm 5 whorls mm 3 whorls mm 4 whorls mm 5 whorls mm 3 whorls mm 4 whorls mm 5 whorls mm Protoconch mm mm mm Microspheric form (B-Form) Diameter Thickness Granulation D= mm T= mm On the septal filaments and between them in juvenile, peripheral in adults D= mm T= mm Scattered on the septal filaments near the periphery D= mm T= mm On the septal filaments near the margin Steps of coiling Lax to tight Tight to lax Tight to lax Number of whorls/radius 24 whorls v mm 26whorls v mm 30 whorls v mm 33 whorls v 14.0 mm 25 whorls v mm 26 whorls v 8.8 mm 30 whorls v 10.4 mm 38 whorls v mm 50 whorls v mm 54 whorls v 21.5-c27.0 mm 50 whorls v mm 58 whorls v 25.6 mm the center. Diameter ranges from 3.1 mm to 6.2 mm. Thickness ranges from 1.2 mm to 2.5 mm. Equatorial section : Steps of coiling tight to lax, septa arched in some individuals sometimes erect at the base, but become gently arched in most of the individuals. The numbers of whorls per radius are as follows : 3 whorls in a radius of 1.4 mm to 2.2 mm, 4 whorls in a radius of 2.2 mm to 2.8 mm and 6 whorls in a radius of 2.8 mm to 3.1 mm. Protoconch diameter ranges from 0.55 to 1.0 mm. Table 3 shows a comparison between N. lyelli morphotype 1, N. lyelli morphotype 2 and N. lyelli Archiac & Haime, (1853). Remarks : The morphotype 2 belong to Nummulites lyelli subgroup. The ontogeny of this species is from tight to lax resembling that of N. lyelli, yet it did not reach the borders of the dimensional data of N. lyelli s.str. Occurrence and stratigraphic distribution : This Nummulites morphotype 2 is collected from sample 6, Mokattam Formation, Citadel section. Age : Late Lutetian. Plate III (Bar scale equals one mm) Figs : Nummulites morphotype 2, sample no. 6, Mokattam Formation, Late Lutetian, Citadel section Figs. 1-4 : Microspheric form, figs. 1-2 equatorial section, figs. 3-4 axial section. Figs : Megalospheric form, figs external view, figs equatorial section, Fig. 29 axial section.

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13 196 M. Boukhary, A. I. Hussein & Y. Hussein-Kamel IV. CONCLUSIONS The rate of evolution of Nummulites species seems to be rapid and it was necessary to group the very related species of Nummulites into phyletic groups carrying common morphological characters and similar structural elements comprising different lineages in the same group. This is clear in the monumental and glorious work of Schaub Three species : Nummulites crassichordatus n.sp., Nummulites morphotype 1 and Nummulites morphotype 2, related to the Nummulitacea, have been recorded from Middle Eocene nummulitic rocks of the sequence cropping our below the Citadel of Salah El Din north of Gebel Mokattam to the east of Cairo. On the basis of the types of coiling, granulation and morphology, Nummulites crassichordatus n.sp. is considered as a member of the N. laevigatus group, the group which has a dense granulation on the surface in which the granules are coalescent. Nummulites morphotypes 1 & 2 belong to N. lyelli subgroup. ACKNOWLEDGEMENTS The authors thank the Late Professor Rene Herb, University of Bern, Switzerland for his valuable comments on N. crassichordatus. A special word of thanks is due to Professor Roland Wernli, University of Geneva, for reviewing the manuscripts and his valuable comments are greatly appreciated. V. REFERENCES Archiac, A.D. & J. Haime (1853) - Description des animaux fossiles, du groupe nummulitique de l Inde. Précédé d un résumé géologique et d une Monographie des Nummulites. Paris. Bitner, M. A. & M. Boukhary (2009) - First record of Brachiopods from the Eocene of Egypt. Natura Croatica, 18 (2) : Blondeau, A. (1972) - Les Nummulites. 1 vol., Vuibert, Paris, 254 p. Boukhary, M.A. (1988) - Nummulites bullatus Azzaroli, 1952, from Egypt and its biostratigraphic significance. Neues Jahrbuch für Geologie und Palaeontologie, Abhandlungen 177/2 : Boukhary, M.A. & Y. Hussein-Kamel (1993) - What is Nummulites gizehensis (FORSKAL) s.str.? Revue de Micropaleontologie, 26 : Boukhary, M.A. & D. Kamal (2003) - What is Nummulites lyelli? Evolution in large foraminifera during the middle Eocene, Egypt. Micropaleontology, 49 (2) : Cuvillier, J. (1930) - Revision du Nummulitique Egyptien. Mémoire, Institut Egypte, Cairo 16 : 371 p. Harpe de la, Ph. ( ) - Etude des Nummulites de la Suisse et révision des espèces éocène des genres Nummulites et Assilina. Mémoire de la Société Paleontologique Suisse, Ire Paris, 7(1881d), 4-102, 2e Partie, ibid. & (1881e), ; 3e Partie (Posthume) ibid 10 (1883a) Hussein, A.I.M. (2003) - Stratigraphic implication of Nummulites basatinensis n.sp. in the Middle Eocene of the Greater Cairo area, Egypt. Fifth International Conference on the geology of the Middle East, Cairo, Egypt : Hussein, A.I.M., M. Boukhary & D. Kamal (2004) - Nummulites farisi n.sp. (Nummulites partschi group) from the Bartonian of El Basatin, Gebel Mokattam, Egypt. Revue de Paleobiologie, 32 (1) : Nuttall, W.L.F. & A.G. Bighton (1931) - Larger Foraminifera from the Tertiary of Somaliland. Geological Magazine, London, 68 : 52. Said, R. (1951) - Restudy of the Races of Nummulites gizehensis. Contributions of the Cushman Foundation Research, Washington 2 : , fig. 9, pl Said, R. & L. Martin (1964) - Cairo area, geological excursion notes. Guide Geol. Archaeol. Egypt, Petrol. Explor. Soc. Libya, 6 th ann. Field conf Schaub, H. (1981) - Nummulites et Assilines de la Tethys Paleogene. Taxonomie, phylogenèse et biostratigraphie. Schweizerische Palaontologische Abhteilung, : 236 p. Shamah, K. & A. Blondeau (1979) - Présence de Nummulites somaliensis dans l Eocène moyen d Egypte. Compte rendu sommaire, Société Géologique de France, 3 : Accepté avril 2010