A new Priabonian Chondrichthyans assemblage from the Western desert, Egypt: Correlation with the Fayum oasis

Journal of African Earth Sciences 61 (2011) 27–37

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A new Priabonian Chondrichthyans assemblage from the Western desert, Egypt: Correlation with the Fayum oasis S. Adnet a,⇑, H. Cappetta a, S. Elnahas b, A. Strougo c a

UMR 5554, ISE de Montpellier, cc 064 Place Eugène Bataillon, 34095 Montpellier Cedex 05, France 15 Elkobba ElGedida Bdg, Entrance 1, Appt. 4, Cairo, Egypt c Ain Shams University, Faculty of Science, Department of Geology, 11566 Cairo, Egypt b

a r t i c l e

i n f o

Article history: Received 20 January 2011 Received in revised form 29 March 2011 Accepted 21 April 2011 Available online 1 May 2011 Keywords: Priabonian Selachian Egypt Western desert Correlations Fayum

a b s t r a c t While the Middle/Late Eocene marine vertebrates in Egypt have been largely reported around the Fayum oasis, few reports were made elsewhere. Here we report a new fossil site (Km55) located near the Bahariya Oasis in the Western desert of Egypt. This fossiliferous outcrop has yielded abundant fossil material of invertebrates dated to the Middle/Late Eocene and some chondrichthyan remains that testify of a Priabonian age (MK11). More than twenty Selachian taxa were recovered in one level, including ‘‘Cretolamna ‘‘ twiggsensis, Misrichthys stromeri, Odontorhytis pappenheimi, ?Jacquhermania attiai, and the fauna is quite similar to some recovered from the Fayum area. However, this new association is clearly distinctive of an open marine environment during the extreme Late Eocene while the contemporaneous fossil sites farther east are deposited in shallower (e.g. Wadi Hitan) or continental environments (e.g. BQ-2). This suggests an E–W diachronous change in relative sea level on the Egyptian coastal shelf during the Late Eocene period, with a general deepening along strike to the West. Ó 2011 Elsevier Ltd. All rights reserved.

1. Introduction Marine Eocene deposits in Egypt are famous both for their fossil content and because they constitute much one of building materials of the Egyptian archaeological treasures from the Cairo area. They consist predominantly in coastal shelfal sandstones and limestones, many with abundant fossil remains. If the marine large foraminifera and invertebrates dominated the fossil assemblage in rocks outcropping around Cairo, many marine Eocene vertebrates were known farther west such as Archaeoceti from the Middle and Late Eocene of the Fayum area (Fig. 1), recently (2005) registered in the UNESCO world Heritage List. In the past much less emphasis has been placed on the Paleogene ichthyofaunas of other localities in the country. Many faunal studies dating from the early 1900s were largely summarized in Case and Cappetta (1990). The largest amount of the selachian teeth described come from the Gehannam Fm. (Late Middle Eocene) and Birket Qarum Fm. (Late Eocene) outcropping in the UNESCO World Heritage Site of Wadi Hitan (formerly ‘‘Zeuglodon Valley’’ in Case and Cappetta, 1990) as recently summarized in Underwood et al. (2011). Some others come from Geziret el Qurun, Qasr ElSagha (Northeastern Fayum) and

⇑ Corresponding author. Tel.: +33 4 67 14 46 52; fax: +33 4 67 14 36 10. E-mail addresses: [email protected] (S. Adnet), henri.cappetta@ univ-montp2.fr (H. Cappetta), [email protected] (A. Strougo). 1464-343X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jafrearsci.2011.04.005

Mokattam hills (Nile valley). No Eocene selachian association was known in the Western desert, to the southwest of the Fayum depression until the work of Strougo et al. (2007) who reported a rich Lutetian selachian association from the ElGedida glauconitic sandstone, located near the Bahariya oasis. The new fossiliferous site which makes the subject of this paper is located at 55 km of the ElGedida-Cairo asphalt road (Fig. 1), on the northern plateau overhanging the Bahariya oasis. Without any conspicuous fixed point (coordinates 28°480 55.0100 N; 29°080 26.4800 E), it is named Km55 in text, in relation to its distance by road from the ElGedida iron mine.

2. Geological setting The bedrock succession having yielded the fossils and presented here, forms a conspicuous butte on the plateau at North of Bahariya Oasis, entirely observable from the road (Fig 2A). The sub-horizontal stratigraphic sequences visible on site Km55 (Fig. 2B) show no obvious syntectonic activity, and is capped by an irregular clastic bed of yellow sandstone. The Paleogene stratigraphic succession exposed in the study area (Fig. 2E) has been initially called the ElHamra Formation by Said and Issawi (1965). Subsequent work has shown that the succession actually comprizes three different units, distinguished by their lithology and fossil content (Strougo, 1986; Strougo and Hottinger, 1987; Strougo and Boukhary, 1987), previously defined

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Fig. 1. Global map showing the location of new fossiliferous locality (large star symbol, Km55) and the previous ones having delivered the main Eocene selachian remains (small star symbol) discussed in text.

in the Fayum area. In the study area, the main characters of these three units are as follows, from base to top: (1) ElGharaq Formation – Mainly bioclastic silty limestones and calcareous siltstones, light colored, white-yellow to yellow green, packed with nummulites, with several thick oyster banks and a large assortment of molluscs. The leading nummulites of this formation are N. gr. gizehensis at the base, followed in the upper part by smaller forms as N. cyrenaicus and N. decrouezae. In the study area, the thickness of the ElGharaq Formation attains nearly 15 m. (2) Birket Qarun Formation. – A 10 m thick, dark-colored unit, consisting of brown, coarse-grained calcareous sandstones, highly fossiliferous, interbedded with dark gray clay. Nummulites are much less abundant than in the lower formation, restricted to the basal part of the unit, and include two species – N. striatus (common) and N. ptukhiani (rare). Two important macroinvertebrates appear at the base of the Birket Qarun Formation, the echinoid Clypeaster fourtaui and the enigmatic hydrozoan(?) Qerunia cornuta. (3) Qasr ElSagha Formation.–As in the Fayum, the lower boundary of the Qasr ElSagha Formation is defined by the first appearance of the large anomid bivalve Carolia placunoides placunoides which occurs in one or more closely spaced prominent banks. The rest of the succession consists of dark brown sandy mudstones and gray clays interbedded with poorly consolidated sandstones. Several monospecific shell beds intercalate the succession either packed with gastropods Mesalia or Turritella or with oysters Ostrea (Turkostrea) multicostata strictiplicata or Nicaisolopha clotbeyi. However, the lower part of the Qasr ElSagha Formation includes a pink sandy limestone layer that yields a very rich and highly diverse macroinverte-

brate assemblage composed of bivalves, gastropods, echinoids, crustaceans, serpulids, and bryozoans. Most importantly, this layer contains numerous examples of Nummulites fabianii, first reported in this area by Strougo and Hottinger (1987). The vertebrate assemblage discussed in this paper was found in a sandy mudstone layer (Fig. 2C–D), about 1 m thick, lying some 10 m above the N. fabianii bed. On top of the Qasr ElSagha Formation comes an interval of crossbedded sandstones and massive, pebbly sandstones, devoid of any fossils, and forming the top of the succession in the study area. A thin layer of conglomerate separates these sandstones from the underlying beds. Whether this interval still belongs in the Qasr ElSagha Formation or to some younger stratigraphic level remains to be seen. Concerning the age of the studied succession which appears thinner than in Fayum area, the ElGharaq Formation of the northern plateau of the Bahariya oasis is generally regarded as marking the upper part of the middle Eocene, that is the Bartonian (Strougo, 1986; Strougo and Hottinger, 1987; Strougo and Boukhary, 1987), whereas the Birket Qarun and Qasr ElSagha Formations are placed in the upper Eocene, that is the Priabonian (Strougo, 1992, 2008). In local chronostratigraphic terms, the nummulite and macroinvertebrate assemblages allow to place the ElGharaq Formation in the middle Mokattamian, and more precisely in the level MK7 of Strougo (2008). Likewise, the Birket Qarun Formation falls in the level MK8. In the Qasr ElSagha Formation, the First Carolia placunoides Biohorizon indicates the level MK9, while the bed with Nummulites fabianii indicates the level MK10. Since the vertebrate assemblage discussed here occurs above the latter bed, it should most certainly be assigned to the level MK11, and, therefore, to a younger part of the Priabonian.

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Fig. 2. A: panoramic view of Km55 (coordinates 28°48’55.01’’N 29°08’26.48’’E); B: focus on sedimentary outcrop, red square indicating the fossiliferous level; C: fossiliferous level (magnificence of red square in B) with selachian teeth; D: observations in situ of a partial disarticulate rib cage (circled by red dashed lines) of a marine mammal. E: Stratigraphic log of the Eocene succession at locality km 55. Asterisk indicates the horizon with selachians and other fossil vertebrate remains. Abbreviations: SS: Sandstone, LS: Limestone. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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3. Material and methods Fossil material was collected by surface picking and dry sieving in the field. Approximately 60 kg of sediment was sieved to 0.4 mm. The selachians represent the largest part of fossil vertebrates remains recovered in locus with about five hundred complete and broken specimens collected. Fossil selachian association currently consists of isolated teeth belonging to 22 fossil species. Among them, the Carcharhiniformes and Myliobatiformes are the most diverse orders. Some of the species are undoubtedly new but they will not be described here because the fossil material is actually judged too scarce, denying a correct evaluation of morphological variability of teeth. Further collecting will be necessary to significantly increase the fossil sample. This study has therefore concentrated on discussions on significant taxa regarding fossil record, dating interest and correlation. However most all the selachian taxa are figured and briefly discussed here. One other taxonomic group of vertebrate was discovered in situ and are some isolated bones or semi-articulated skeletons of marine mammals (probably belonging to sea cow) that were observed in the level (Fig. 2D) where the selachian teeth were recovered. Further field work will be necessary to compare these fossil remains with the diverse faunas in the Fayum depression from during the contemporaneous times (Gingerich, 1992; Uhen, 2004; Peters et al., 2009). The material is deposited at the Laboratory of Paleontology, ISE of Montpellier. Abbreviations: BAH: collection number for material from Bahariya, Km55. 4. Systematic palaeontology

Order Lamniformes: ?F. ‘‘Cretoxyrhinidae’’ ‘‘Cretolamna’’ twiggsensis (Case, 1981), Fig. 3A 1905. Otodus cf. aschersoni – Stromer, pl.15, Fig. 13 1905. Lamna cf. vincenti – Stromer, pl.15, Figs. 24 and 25 1905. Odontaspis cf. cuspidatus – Stromer, pl.15, Fig. 26 1981. Lamna twiggsensis – Case, pl. 3, Figs. 3–8 1990. Cretolamna twiggsensis – Case & Cappetta, pl. 3, Figs. 40– 55 1991. Cretolamna twiggsensis – Case & West, Pl. 1, Fig. 1 2000. Cretolamna twiggsensis – Case & Borodin, pl. 2, Figs. 13– 19 2007. Cretolamna twiggsensis – Adnet et al., Figs. 6.21 and 6.22 2010. ‘‘Cretolamna’’ twiggsensis – Adnet et al., Fig. 3c 2011. Brachycarcharias twiggsensis – Underwood et al., Fig. 4L– M

Teeth are rather large; the cusp is high, quite triangular in upper teeth and not very thick. The root lobes are elongated and their extremities are often rounded. If there is only one pair of marginal denticles in anterior teeth, the lateral ones (Fig. 3A) are characterised by two pair of marginal denticles, the proximal pair are triangular and the distal pair are much smaller and accurate. This reduced material belongs without doubt to the species ‘‘C.’’ twiggsensis, even if its attribution to the genus Cretolamna is sometimes refuted (Underwood et al., 2011). It should be probably assigned to a new lamniform genus. This species was previously recovered in Egypt (from Mokkatam to Wadi Hitan), both in Bartonian and Priabonian deposits (see Case and Cappetta, 1990 and Underwood et al., 2011 for discussion). This fossil species is recorded elsewhere from Pakistan (Adnet et al., 2007), Southwestern Morocco (Adnet

et al., 2010) and Georgia, USA (Case, 1981; Case and Borodin, 2000). Such occurrences suggest this neritic species may have been confined to the tropical Tethys during the Bartonian–Priabonian period. This species was assigned to the genus Brachycarcharias by Underwood et al. (2011). However, important morphological differences can be noted; in ‘‘C.’’ twiggsensis, there are usually two pairs of lateral cusplets in anterior and lateral teeth, contrary to what is observed in Brachycarcharias like for instance B. lerichei (see Cappetta and Nolf, 2005). Moreover, teeth of ‘‘C.’’ twiggsensis have a completely smooth enameloid, that is not the case of Brachycarcharias, in which folds occur usually on the lingual face of the crown. The attribution to a new genus belonging to Odontaspidid or Cretoxyrhinid seems obvious but is out of scope of this work, awaiting more material and further analysis. Order Carcharhiniformes: F. Carcharhinidae Misrichthys stromeri Case and Cappetta, 1990, Fig. 3B–C 1905. Carcharias sp. indet. – Stromer, pl. 16, Figs. 20 and 21 1990. Misrichthys stromeri – Case and Cappetta, 1990, pl.5, Figs. 108–112; pl.6, Figs. 113–140; pl.7, Figs. 141–142 2010. Misrichthys stromeri – Murray et al., Fig. 1C 2010. Misrichthys stromeri – Adnet et al., Fig. 3f 2011. Misrichthys stromeri – Underwood et al., Fig. 4O

This large species displays a clear dignathic heterodonty. The upper teeth (Fig. 3B) have a high triangular cusp, distally inclined in antero-lateral and lateral files. The mesial cutting edge is unserrated, convex and not or slightly distinct from the mesial heel. The distal cutting edge is unserrated, concave and well separated from the short rounded distal heel, sometimes angular, by a notch; except on the more anterior teeth. Root is high with divergent lobes and a median groove. The lower anterior teeth (Fig. 3C) have a high and narrow cusp, the cutting edges are well marked but never reach the shortly and abrupt heels. The root is massive with a well developed lingual protuberance bearing a very deep nutritive groove and two short lobes. Enameloid of crown is totally smooth both on lower and upper teeth. This monospecific genus was solely restricted to Egypt (Case and Cappetta, 1990; Murray et al., 2010; Underwood et al., 2011) until its discovery in contemporaneous deposit from South-western Morocco (Adnet et al., 2010). Moreover, it also occurs in the Late Eocene of Tunisia (S.A. pers. observ.). Murray et al. (2010) compared the biology of Misrichthys stromeri to the living tropical species Carcharhinus leucas which has an ability to tolerate the brackish to fresh water. One tooth of Misrichthys stromeri was found below the top bed composed by a conglomerate rock (Fig. 2B), approximately ten meters above the fossiliferous level. Carcharhinus sp.1, Fig. 3D–F 1905. Carcharias (Prionodon) cf. egertoni – Stromer, p. 177, pl. 16, Figs. 17 and 18 1991. Carcharhinus sp.1 – Case & Cappetta, p. 12–13, pl.7, Figs. 164 and 165 2010. Carcharhinus sp. – Adnet et al., Fig. 3g 2011. Carcharhinus sp. – Underwood et al., Fig. 4N

The species displays a distinct dignathic heterodonty. Teeth are large, reaching up to 15 mm high. In upper jaw, teeth (Fig. 3D and F) show a cusp distally curved, the mesial heel is lacking in lateral teeth (Fig 3D.1) and few developed in first and anterior teeth (Fig. 3F). Cutting edges are strongly and regularly serrated from the lateral extremities to the apex of cusp. The crown/root boundary of the lingual face is marked by a free-enamel tape or chevron

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Fig. 3. A. (BAH-1): ‘‘C’’ twiggsensis, 1. lingual view, 2. labial view; B–C: M. stromeri, B. (BAH-2) upper antero-lateral tooth 1. lingual view, 2. labial view, C. (BAH-3) lower anterior tooth,1. lingual view, 2. labial view; D–F: Carcharhinus sp. 1, D. (BAH-4) upper lateral tooth, 1. lingual view, 2. labial view, E. (BAH-5) lower antero-lateral tooth, lingual view, f. upper antero-lateral tooth, lingual view; G–H: C. aff. frequens, G. (BAH-6) lower anterior tooth, lingual view, H. (BAH-7) upper antero-lateral tooth, labial view; I–M: Carcharhinus sp. or Negaprion sp., I. (BAH-8) upper anterior tooth, 1. lingual view, 2. labial view, J. (BAH-8) upper antero-lateral tooth, labial view, K. (BAH-9) upper antero-lateral view, labial view, L. (BAH-10) lower anterior tooth, labial view, M. (BAH-11) lower antero-lateral tooth, 1. labial view, 2. lingual view; N–O: ?Sphyrna sp. N. (BAH-12) antero-lateral tooth, 1. labial view, 2. lingual view, O. (BAH-13) lateral tooth, labial view; P–Q: Rhizoprionodon sp. P. (BAH-14) antero-lateral tooth, 1. labial view, 2. lingual view, Q. (BAH-14) lateral tooth, 1. lingual view, 2. labial view; R. (BAH-15) Scyliorhinus sp. 1, lateral tooth, 1. occlusal view, 2. mid-profile view; S.(BAH-16) Scyliorhinus sp. 2, antero-lateral tooth, 1. occlusal view, 2. basal view; T.(BAH-17): O aff. pappenheimi, 1. profile, 2. labial view.

(Fig. 3D.2–3, 3F), according the teeth considered. Root is massive and high with short lobes separated on the lingual face by a wide and deep nutritive groove. The nutritive foramen opens in the upper part of groove. Teeth of this species remind those of living species as C. obscurus or C. plumbeus belonging to the named ‘‘Bull-shark’’ group as explained in Case and Cappetta, 1990. Even if this tooth shape is probably convergent among the Carcharhinus lineage (Naylor, 1992), very few records of this group are known in the Palaeogene, contrary to Neogene (see Purdy et al., 2001). Palaeogene Carcharhinus of this type are known only from

the Late Eocene-Early Oligocene of Pakistan (Adnet et al., 2007), the late Middle Eocene of Zeuglodon Valley (Case and Cappetta, 1990; Underwood et al., 2011) and the late Middle Eocene-Late Eocene of Southwestern Morocco (Adnet et al., 2010). Material from Km55 is quite similar to those previously recovered in Middle-Late Eocene (Carcharhinus sp. 1 in Case and Cappetta, 1990, Carcharhinus sp. 1 in Underwood et al., 2011) and Southwestern Morocco (Carcharhinus sp. in Adnet et al., 2010). Contrary to Adnet et al. (2007) who suspected an origination in eastern Tethys during the Late Eocene, these modern carcharhinids frequented the North

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African coasts too. No contemporenaous record was signalled outside this tropical area. Carcharhinus aff. frequens (Dames, 1883), Fig. 3G–H 1905. Carcharias sp. – Stromer, pl. 16, Figs. 21 and 28 1908. Carcharias (Aprionodon) aff. frequens – Priem, pl.15, Fig. 6–7 1971. Aprionodon frequens – Casier, pl. 1, Fig. 6 1990. Carcharhinus frequens – Case & Cappetta, pl. 5, Figs. 102– 107; pl.7, Figs. 143–148 and 151–159 2011. Negaprion sp. – Underwood et al., Fig. 5T–U

The species displays a moderate but well marked dignathic heterodonty. The upper teeth (Fig. 3H) have a crown of triangular outline with a cusp slightly slanted distally. The cutting edges are always unserrated and are not disconnected from the cutting edges of lateral heels which are totally smooth on our material. Root is relatively flat and elongated mesio-distally. The lower teeth (Fig. 3G) have an erect cusp with smooth cutting edges than never reach the heels, except on some lateral teeth. The root lobes have enlarged and rounded extremities. Median nutritive groove of root is well-marked on upper and lower teeth but it is relatively shallower than in the other Carcharhinus species. Case and Cappetta (1990, p. 12) have largely reviewed the fossil record of this species which is attributed to the genus Negaprion by Underwood et al. (2011). Our scarce material does not allow to discuss about this taxonomic divergence. However, the discontinuity of the cutting edge between the cusp and the heels in lower anterior and antero-lateral teeth does not favor an attribution to Negaprion. Such tooth shape better fits with Carcharhinus as living C. isodon (Müller & Henle, 1838) or to a lesser extent to C. limbatus (Müller & Henle, 1838). C. frequens is currently known from the late Middle Eocene-Late Eocene of Qatar (Casier, 1971) and Southwestern Morocco (Adnet et al., 2010) until the Late Eocene of the Fayum Oasis (Case and Cappetta, 1990; Underwood et al., 2011) where it dominates the faunal assemblages from the sandstones of the Birket Qarun Fm. (Underwood et al., 2011). Carcharhinus sp. or Negaprion sp, Fig. 3I–M ?1990. Carcharhinus sp. 2 – Case & Cappetta, pl. 8, Figs. 176 and 177 2010. Carcharhinus sp. – Murray et al., Fig. 1.D 2011. Negaprion frequens – Underwood et al., Fig. 5V–W

The species displays a distinct dignathic heterodonty. The upper teeth (Fig. 3I–K) have a broad labiolingually compressed triangular cusp that is distally inclined in lateral files (Fig. 3K). Enamel of crown is smooth except on the basal edge of the labial face where slight vertical folds may be observed on large upper (Fig. 3I and J) and lower teeth (Fig. 3L). The cutting edges of the cusp are principally convex and totally unserrated, except on the lateral heels of upper teeth where they may be slightly serrated (Fig. 3J and K). There are distinct notches that separate the two cutting edges from the rounded serrated heels. Root is subquadrangular and lobes are separated by a deep well-developed groove that forms a basal notch in labial view. Morphology of this taxon reminds those from Locality BQ-2 (Murray et al., 2010) and Gar Gehannam Fm. (Case and Cappetta, 1990 as Carcharhinus sp. 2) in having a smooth cusp and serrated heels. The scarcity of the material recovered elsewhere (one tooth per sites) does not allow a further comparison with our material, especially concerning the labial folds on the crown enamel that are

lacking in some specimens. These dental features remind those of C. gibbesi (Woodward, 1889), known in the Oligocene deposits from North America (see Cicimurri and Knight, 2009) but our specimens are distinguished by a serration of heels even more slight and some enamelled folds on basal edge of the crown. Underwood et al. (2011) reported similar material as N. frequens (Dames, 1883). Attribution to the genus Negaprion is tenable in regard of extant species N. brevirostris (Poey, 1868) but species is clearly different from Aprionodon frequens described by Dames (1883) that we consider as belonging to Carcharhinus . Rhizoprionodon sp., Fig. 3P–Q 1990. Rhizoprionodon sp. – Case & Cappetta, pl.7. Figs. 160– 163 ?1991. Rhizoprionodon sp. – Case & West, pl. 3. Figs. 2–4 2007. Rhizoprionodon sp. – Adnet et al., Fig. 6.10

The teeth are small, the cusp is long in anterior files (Fig. 3P) and short and slanted distally in more lateral files (Fig. 3Q). The mesial cutting edge is convex, totally smooth and runs from the mesial crown extremity to apex of cusp without interruption. The distal cutting edge is short and concave and well-separated from distal heel by a notch. The distal heel is rounded to angular and bears sometimes an obtuse denticle. Root is flat, sub-rectangular and elongated mesio-distally. This genus is relatively common in worldwide Eocene marine deposits, Egypt included (Case and Cappetta, 1990; Strougo et al., 2007; Underwood et al., 2011) but few species have been identified because the teeth display a quite homogeneous morphology through geological times and only the unquestionable attribution to the genus can be made. The distinction of species is currently difficult to assess, especially when material is scarce. As for the unnamed species from Pakistan (Case and West, 1991; Adnet et al., 2007), material appears to be more closely related to the Oligocene specimens from North America. F. Sphyrnidae: ?Sphyrna sp. Fig. 3N–O ?2011. Rhizoprionodon sp. – Underwood et al., Fig. 5O–P

Only two teeth are currently reported to ?Sphyrna sp. The cusp is relatively thick and short in mesio-distal axis; the cutting edges lack serration and the mesial cutting edge is straight (Fig. 3O) to slightly concave (Fig. 3N). Distal heel is well developed, rounded and completely unserrated. Root is broader than crown both in antero-lateral teeth (Fig. 3N) and lateral ones (Fig. 3O); root lobes are well aligned, horizontal and separated by a straight and deep nutritive groove. Teeth remind those of the living species S. media Springer 1940 as possibly figured at the fossil state by Genault (1993) from the Chattian of France and Cicimurri and Knight (2009, Fig. 5K) from the Rupelian of South Carolina. However isolated teeth of Sphyrna are hardly distinctive from Rhizoprionodon, and the scarcity of our material justifies our affiliation only. Underwood et al. (2011) do not report the presence of Sphyrna in the Fayum area but they mention two morphs as Rhizoprionodon in the text, figuring the more robust one (Underwood et al., 2011: Fig. 5O–P) that approching the tooth morphology of the hammerhead Sphyrna. The earliest appearance of hammerhead sharks is Oligocene (Dutheil, 1991; Genault, 1993; Adnet et al., 2007; Cicimurri and Knight, 2009) but its stratigraphical range should be probably extended to the Late Eocene in Egypt if its generic attribution was confirmed. The scarcity of the material does not allow a more precise attribution.

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F. Scyliorhinidae: Scyliorhinus spp., Fig. 3R–S Fossil material attributed to Scyliorhinidae is reduced to rare and broken teeth of small size. However two distinct morphologies of teeth are easily differentiable and they were assigned to two unnamed Scyliorhinus species, awaiting more specimens. First species, Scyliorhinus sp. 1, is only known at Km55 by one tooth (Fig. 3R) with dissymmetric cusp flanked of two linguo-laterally lobes which are rounded, well-detached and overhanging a thick root. It could remind tooth figured by Underwood et al., 2011 as Leptocharias sp. but root is thicker and no lateral

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denticle nor ornamentation of enamel are visible on the crown. The second species, Scyliorhinus sp. 2 (Fig. 3S), represented by a unique specimen, has tooth smaller than Scyliorhinus sp.1. Tooth is bend distally, the median cusp is well-developed and flanked by a pair of lateral small cusplets as observed in Fayoum specimens (Underwood et al., 2011 Fig. 6M). Numerous folds are strongly marked on the enamel of the labial face of crown, from the base to the mid high of cusp. Lingual face of crown is smooth. Root is not developed lingually as in the previous species.

Fig. 4. A. (BAH-18): ?Propristis sp., oral tooth 1. lingual view, 2. profile, 3. occlusal view; B. (BAH-19): ?Pristis sp., oral tooth, 1. lingual view, 2. profile; C–D: Rhinobatos sp., C. (BAH-20) lateral tooth, 1. lingual view, 2. occlusal view; D. (BAH-21) anterior tooth, 1. lingual view, 2. profile, 3. basal view; E: Rhynchobatus sp., lingual view; F-H: Pastinachus sp. F. (BAH-22) anterior tooth, 1. lingual view, 2. labial view, 3. occlusal view, G. (BAH-23) antero-lateral tooth, 1. lingual view, 2. profile, 3. labial view, 4. basal view, 4. occlusal view, H. (BAH-24) lateral tooth, 1. lingual view, 2. profile, 3. labial view, 4. (BAH-25) occlusal view; I: Dasyatis sp., 1. lingual view, 2. labial view; J–K. (BAH-26, 27): Taeniura sp., lingual view; L–N: Ouledia sp., L. (BAH-28) young specimen, lingual view; M. male, lingual view, N. (BAH-29) female, profile; O (BAH-30): ?Jacquhermania attiai, semi-lingual view; P. (BAH-31): Coupatezia sp., 1. occlusal view, 2. lingual view.

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Fig. 5. Relative frequency (size of circle) of selachian taxa from Km55 and other Late Eocene localities elsewhere in Egypt [from Murray et al. (2010), Underwood et al. (2011)]. Open circle: uncertain affiliation, black circle: marine taxon, gray circle: marine taxon with possible tolerance to brackish-freshwater environment as exposed in Murray et al. (2010).

Neoselachii incertae sedis: Odontorhytis aff. pappenheimi (Böhm, 1926), Fig. 3T 1905. Percoïd indet. – Priem Figs. 10 and 11 1909. Rajid or Scylliid – Priem, Figs. 34 and 35 1926. Odontorhytis pappenheimi – Böhm, Fig. 17 1990. Odontorhytis pappenheimi – Case & Cappetta, pl. 8, Figs. 166–175 1991. Odontorhytis pappenheimi – Case & West, Fig. 3 2010. Odontorhytis pappenheimi – Murray et al., Fig. 1A–B 2011. Odontorhytis pappenheimi – Underwood et al., Fig. 5Z, AA, BB

This taxon is the most abundant of the fossil association of Km55. The teeth are relatively large (up to 15 mm of total height), symmetrical and flattened mesio-distally. The cusp is high, only the labial face bears a salient median cutting edge from the base to the top of the cusp curved lingually. The lingual face shows a distinct barb in its apical part (Fig. 3T.1). The apparently very thin enamel of crown is covered by numerous parallel folds, both on the lingual and labial face, which have not distinct boundaries. Some teeth are more slender than others but no variation of shape was really detected among the teeth of various sizes. Easily differentiable from the Ypresian species from Morocco (Cappetta, 1981), the morphology of Egyptian teeth are rather similar to those of O. pappenheimi known from Middle-Late Eocene in several localities from Africa (see Cappetta, 1987), possibly in Pakistan (Case and West, 1991) and reported from the Fayum depression (Case and Cappetta, 1990; Murray et al., 2010; Underwood et al., 2011). However the teeth are twice as large justifying only provisional affiliation, waiting for further investigation about this enigmatical taxon. Strougo et al. (2007) already figured an Odontorhytis tooth from Western

desert (Bahariya oasis, Lutetian) but their teeth are smaller, more slender and devoid of linguo-apical barb compared to those reported here. O. pappenheimi teeth are mainly found in shallower marine water sediment and this genus probably could tolerate relatively brackish water as reported in Murray et al. (2010). Order Rajiformes: F. Pristidae Only the oral teeth were found in site Km55, leading questionable any comparison with contemporaneous Pristids (sawfish) which are essentially known by their large rostral spines. At least 4 species of Pristids are known elsewhere in Egypt during the Bartonian–Priabonian period: Anoxypristis aff. mucrodens, Pristis lathami, P. fayumensis and Propristis schweinfurthi (see Case and Cappetta, 1990, Underwood et al., 2011). Further information and material are necessary to correctly attribute these oral teeth to one or other Pristids. Murray et al. (2010) and Underwood et al. (2011) suspected the presence of another unknown pristid (attributed in part to P. fayumensis) in Late Eocene (upper part) of Birket Qarun and lower part of Qasr ElSagha Fm. Based on rostral spines that seem smaller and slender, this new occurrence must be now confirmed even if we still ignore if they represent P. fayumensis or the new species. Two morphological types have been identified in material. The first one, gathering the smaller teeth (attributed to Pristidae or Rhinobatidae indet. in Underwood et al., 2011) were tentatively attributed as ?Propristis sp. (Fig. 4A). Oral teeth are very small, reaching up to 1.5 mm maximal size. The teeth are broader than long; the crown is relatively high with an erected cusp marked by a sharp transversal crest and two shortly lateral uvulae. Root is rather thin, compressed mesiodistally but longer than crown. The margino-lingual faces are flat, regular and do not form any lingual extension under the median uvula of crown. We suspect an affinity of these teeth to Propristis because their morphology seems different to those of genera Anoxypritis or Pristis, both from fossil (in Underwood et al., 2011, Fig. 6Q–T) and living representatives (Herman et al., 1997).

S. Adnet et al. / Journal of African Earth Sciences 61 (2011) 27–37

The second group gathers the largest teeth and was attributed to Pristis sp. (Fig. 2B). Oral teeth look like those of the previous Pristidae but are longer than latter, reaching up to 2 mm high. Compared to the previous species, root is more massive in lingual or lateral view (Fig. 2B2). Uvula is stronger and lingually developed. Root is higher than crown and the margino-lingual faces display a lingual extension delimited by two large foramina. These large teeth could be referred to genus Pristis according figures of Herman et al. (1997) or Underwood et al. (2011). F. Rhinobatidae and F. Rhynchobatidae: Rhinobatos spp. Morphology of teeth is close to those of Pristid (oral teeth). They differ by longer teeth with root lower and more developed lingually. The median uvula is longer, convex in profile and often overlies the lingual extremity of root groove. The medial protuberances of the root lobes are often more salient and strongly developed lingually. As ‘‘Rhinobatos’’ includes a number of extant species with tooth morphology unknown (Cappetta, 1987), fossil forms are often unnamed, awaiting further analysis. Material provisionally attributed to Rhinobatos sp. (Fig. 4C and D) differs from those of ElGedida (Strougo et al., 2007, Fig. 2.3) in having more distinct uvulae in anterior and lateral teeth, two root lobes more salient lingually. There is significant difference in size of teeth (and sometimes in morphology) inside our small sample that could be related to the presence of several species. Rhynchobatus sp. (Fig. 4E). Scarcity of material does not authorize a more precise determination, particularly in comparison with the three unnamed species occurring in Fayum (Underwood et al., 2011). Order Myliobatiformes: F. Dasyatidae Numerous teeth could be assigned to dasyatid species. At least three distinct taxa were identified on tooth morphology. One of them is quite unusual in fossil record and was identified as Pastinachus. Some of them were identified as Dasyatis or Himantura sp. (Fig. 4I). Teeth are relatively large and massive, crown is longer than broad and enamel is not or little ornamented. Labial face is rounded in profile. Several teeth show some difference in morphology and have been attributed to ?Taeniura sp. (Fig. 4J and K). Labial face of crown is convex between a narrow transversal keel (often eroded, Fig. 4K) and the labial edge of crown where the enamel surface is irregular. The enameloid surface of the lingual face is smooth, excepted around the transversal keel where there are some poorly developed costules. Root is strongly dejected lingually; root lobes are relatively flat with a triangular outline in basal view. No sexual dimorphism was detected in our material. These teeth closely resemble those of the Recent species Taeniura grabata, as figured in Herman et al. (1998). Contrary to most of the other Dasyatidae (e.g. Dasyatis or Himantura) teeth possess a convex labial face, a thin ornamentation of enamel and no sexual dimorphism. Indeed, they were provisionally attributed to genus Taeniura. The difference in tooth morphology among the Dasyatidae remains tenuous and further analyses are necessary to provide some distinctive keys (see Cappetta, in print).

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antero-lateral teeth (Fig. 4 G) have a rounded and more massive crown with a rhombic outline in occlusal (Fig. 4G.5) or basal view (Fig. 4G.4). The more lateral teeth (Fig. 4H) are similar to the previous ones, except that they are larger and strongly elongated in a mesio-distal axis. Such peculiar heterodonty was recently illustrated for the living species Pastinachus solocirostris in Last et al. (2005). Detailed dental anatomy of this peculiar genus was illustrated by Herman et al. (1998) and is described by one of the senior authors (Cappetta, in press). Confusion with the palaeogene genus Hypolophodon (Cappetta, 1980) is possible due to the uncommon morphology of lateral teeth for a Dasyatid. But teeth of Hypolophodon should not interlock between themselves or slightly (Cappetta, 1980, p. 41) because there is no transversal furrow or bulge on lingual and labial face of crown, respectively. Living representatives of Pastinachus (formerly Hypolophus in Müller and Henle, 1837) are known to be amphidromous, frequenting the marine, brackish to freshwater (P. sephen at least) of the Indopacific area. We reserved our determination because there are some minor differences in fossils concerning the root morphology, being more massive, rounded and vertical than in the living species observed. Dasyatoid incertae sedis: Coupatezia sp., Fig. 4P 2010. Coupatezia woutersi – Murray et al., Fig. 2B 2011. Coupatezia sp. – Underwood et al., Fig. 7D–E

Contrary to Murray et al. (2010), we did not assign these teeth to the Lutetian species Coupatezia woutersi Cappetta, 1982, which must be restricted to the European middle Eocene as recommended by Cappetta (1982). This was not assigned to species by in Underwood et al. (2011) and probably new species is different from those of the Middle Eocene of Bahariya oasis (Strougo et al., 2007) in having a non ornamented labial face. F. Gymnuridae: Ouledia sp.,Fig. 4L–N 2011. Ouledia sp. – Underwood et al., Fig. 7J

The smallest teeth of our selachian assemblage belong to Ouledia sp. (Fig. 4L–N). The teeth are different from those of the Early Eocene species O. sigei Cappetta, 1986 in having a lower crown and root lobes more massive and closer. This genus seems to be rather common in worldwide tropical sea during the Middle-Late Eocene period because it is recovered in shallow water deposits from Southwestern Asia (Adnet et al., 2008), India (see Adnet et al., 2008), Egypt (Strougo et al., 2007; Underwood et al., 2011) and Morocco (Tabuce et al., 2005; Adnet et al., 2010). Similar to the unnamed species of Fayum (Underwood et al., 2011, Fig. 7J), morphology of teeth is close to those from Bahariya (Strougo et al., 2007, pl.3.7) or from Myanmar (Adnet et al., 2008, Fig. 2.3– 4). Differences between all the specimens from Asia to Morocco are really tenuous and supplementary material is waiting for further analysis.

Pastinachus sp.: Fig. 4F–H 2010. Hypolophodon cf. H. malembeensis – Murray et al., 2010, Fig. 2.C and D 2011. Pastinachus sp. – Underwood et al., Fig. 5DD–FF, Fig. 7L

?Jacquhermania attiai: (Cook, in Murray et al., 2010), Fig. 4O 2010. Coupatezia attiai – Murray et al., 2010, Fig. 1G, 2A 2011. ?Jacquhermania attiai – Underwood et al., Fig. 7F–G

The species displays a strong monognatic heterodonty with a size ratio near 1/5 between anterior and lateral teeth. The anterior teeth (Fig. 4 F) are small with a high crown displaying a dissymmetric outline and a strongly undulating occlusal face. The

Cook, in Murray et al. (2010), has recently described this new species from the Fayum depression. Crown is especially high and remarkably circular in occlusal view. Oral face is convex and well-delimited by a fine circular crest which lacks in the labial part. Enamel of crown is totally free of ornamentation and the bilobate

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S. Adnet et al. / Journal of African Earth Sciences 61 (2011) 27–37

root is massive, rounded and at least as high as the crown. As correctly observed by Murray et al. (2010), this species should be removed from Coupateza and given a new genus. However we suspect an appartenance to Gymnuridae instead of Dasyatoid because teeth are often mesiodistally compressed and display a root which sometimes protudes lingually the crown in occlusal view. These features remind those of an Eocene gymnurid: Jacquhermania (Cappetta, 1982) justifying the provisionally placement in that genus, in agreement with Underwood et al. (2011). F. Rhinopteridae Some rare teeth recovered in Km55 remind those of R. sherboni White, 1926 recovered in Priabonian of Fayum (Murray et al., 2010, Underwod et al., 2011) in having a thin root and no ornamentation on the occlusal face of crown. However our material is relatively damaged and does not allow to precise a specific attribution. 5. Correlation, Dating interest and paleoenvironment 5.1. Dating interest Comfortably dated to the upper part of the upper Mokattamian (MK11) according to stratigraphic position and macroinvertebrate association (Strougo and Hottinger, 1987; Strougo, 2008), the selachians found in the northern plateau of the Bahariya oasis appear to belong in the upper part of the Priabonian (Fig. 5). Underwood et al. (2011) summarized the biostratigraphical changes of the Middle/Late Eocene selachians recovered in Egypt. Their main conclusion is that most of the changes in the relative frequency of sharks and rays are likely to be environmentally controlled. However, they remarked that, even though numerous taxa must be further described, the appearance of ‘‘Cretolamna’’ twiggsensis s.s., ?Jacquhermania attiai and Pastinachus sp. in confirmed Priabonian levels could be regarded as biostratigraphically useful taxa. Their presence at Km55 provides a supplementary support for a Priabonian age and for correlation with the Qasr ElSagha Formation in the Fayum. 5.2. Faunal comparisons and paleoenvironment Detailed comparisons between Egyptian localities can be considered (Fig. 5). The selachian fauna of Km55 shows a great similarity with the other Middle/Late Eocene fauna recovered in the Fayum (Wadi Hitan, Qasr ElSagha). Precise comparison with the faunal associations from Qasr ElSagha, as reported in Case and Cappetta (1990), is currently irrelevant because most of them came from old samples which were limited to the surface collecting of macrofossils in many imprecise localities (Case and Cappetta, 1990, p. 3) and age. Underwood et al. (2011) reported the first complete list of selachian taxa recovered inside the UNESCO World Heritage Site of Wadi Hitan, the most western fossiliferous locality of the Fayum Oasis (see Fig. 1). A part of this fauna comes from shallow marine sandstones and mudstones belonging to the Gehannam Fm. (level D-G) and the Birket Qarum Fm. of Wadi Hitan (Underwood et al., 2011 – Tab.1 & 2) and dated at least to the Early Priabonian. These levels are stratigraphically overlain by varied deposits of the Qasr ElSagha Fm., which have delivered numerous fossils in the lower (‘‘channel base’’) and upper parts (‘‘Interdune lag’’). The whole selachian fauna comprises more than 90 taxa and remains understudied in detail; the comparison is thus often limited at the supra-specific level (Fig. 5). Seventeen of the twenty taxa recovered at Km55 are shared with levels of the Birket Qarun Fm. of Wadi Hitan. Proportions of common taxa are lower with associations recovered in the levels D-G from the Gehannam Fm. (11/20), the lower part of the Qasr ElSagha Fm. (16/20) or its upper part (10/20), though closer to Km55 in age. This incongruence is

partially due to the ecological difference between the fauna of Km55 and those of localities of Wadi Hitan belonging to the two members of the Qasr ElSagha system. The lower part (‘‘channel base’’) was first considered as fully deposited in freshwater environments (Gingerich, 1992; Peters et al., 2009, 2010). Underwood et al. (2011, in press) revised this point of view and considered that the selachian fauna was probably deposited in large tidal channels as the significant part of open marine forms testifies. The depositional environment of the upper part of the Qasr ElSagha system in Wadi Hitan is conflicting and more uncertain (see Peters et al., 2010 vs. Underwood et al., in press) but clearly shallower than in the lower part. Our faunal associations testify that Km55 was clearly under marine influence compared with contemporaneous localities of the Qasr ElSagha system in Wadi Hitan and quite comparable to environmental conditions of older sites belonging to the upper part of the Gehannam Fm. or to the Birket Qarum Fm. (Early Priabonian). The faunal association of Km55 indicates that the major fall in relative sea level suggested by Peters et al. (2009, 2010) in Wadi Hitan area during the Priabonian cannot be confirmed 100 km further to the southwest. All the eight selachian taxa recovered in locality BQ-2 in the Fayum (Murray et al., 2010) are common with those from Km55, in agreement with a Priabonian age too. Nevertheless, our fauna may be somewhat younger because BQ-2 has been placed in the Birket Qarun Formation and dated to the Early Priabonian (Seiffert, 2006 ; Murray et al., 2010) and, hence, should fall in the level MK8. It must be remarked, however, that Underwood et al. (2011) put forward some paleontological evidence suggesting that Locality BQ-2 would better be correlated with the Qasr ElSagha Fm. Differences in faunal association with BQ-2 are however obvious as the greater abundance of sharks (especially the Carcharhinidae) in Km55, the larger diversity of batoids (e.g. Rhinobatidae, Rhynchobatidae, Dasyatidae, Gymnuridae), and the virtual absence of frankly fresh water elements in Km55 (such as freshwater teleosts). As previously mentioned, these probable ecological differences attest of a more marine environment of deposition at Km55 than BQ-2. This preliminary result suggests a diachronic change in relative sea level in the Egyptian basin from East to West with an ending of marine influence at the Early Priabonian (MK8) on eastern Fayum (BQ-2), during the Priabonian (MK8-11) on western Fayum (Wadi Hitan, ‘‘interdune lag’’ system of Qasr ElSaghr Fm.) or younger than Mid-late Priabonian (MK11) at 100 km west of Fayum (Km55).

Acknowledgements The authors wish to thank C. Underwood (London) and an anonymous reviewer for their critical reading of the manuscript and very helpful suggestions. This research was supported by the French ANR-PALASIAFRICA Program (ANR-08-JCJC-0017, ANRERC) and by the Geology Department of the Ain Shams University. ISEM No. 2011-034.

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