Return to Dor al-Talha - Springer Link

Return to Dor al-Talha Paleontological Reconnaissance of the Early Tertiary of Libya D. Tab Rasmussen, Sefau O. Tshakreen, Miloud M. Abugares and Joshua B. Smith

Introduction No individual has contributed more to the growth of knowledge about mammalian evolution in the Early Tertiary of Africa than Elwyn Simons. For 45 years he has steadfastly worked the Fayum sites, and the efforts of his field teams have yielded an incredible richness of paleontological treasures. Referring to the Egyptian sites by the monolithic term ‘‘The Fayum’’ does not do justice to the diversity of fossil localities contained within the research area. Simons and his colleagues have developed quarries at multiple stratigraphic levels within the early Oligocene, the late Eocene, and in recent years, the middle Eocene (Simons, 1968; El-Kashab et al., 1983; Simons and Rasmussen, 1995; Seiffert et al., 2003, 2005, 2008; Seiffert, 2006). These localities include several famous vertebrate-bearing sites, but also ones that yield fossil terrestrial plants, ichnofossils, and invertebrates (Wing and Tiffney, 1982; Bown et al., 1982; Bown and Kraus, 1988). His forays into neighboring marine Eocene and early Miocene sites have fostered research in those areas as well (e.g., Gingerich, 1992, this volume; Miller, 1999). In sum, the Fayum project represents the most important natural laboratory on the African Early Tertiary in terms of temporal span covered, taxonomic diversity represented, completeness of skeletal remains, and the richness of accompanying paleobiological and paleoecological research. The research led by Simons also has been important in illuminating paleontological work at other, non-Egyptian Early Tertiary sites of the Arabian-African continent. In the early 20th Century, the Fayum provided the first glimpse of the archaic, endemic mammal faunas of Africa (Andrews, 1906; Osborn, 1908; Schlosser, 1911; El-Kashab et al., 1983). Now, many decades later, similar Early Tertiary mammals have been found at a handful of sites in Mali, Algeria, Tunisia, and Oman (e.g., Mahboubi et al., 1986; Rasmussen et al., 1992; Thomas et al., 1999; Gheerbrant et al., 2002). The Fayum’s magneto- and biostratigraphy has proven to be a central axis by which to compare other African sites D. Tab Rasmussen Department of Anthropology, Washington University, St. Louis, MO 63130, USA [email protected]

J. G. Fleagle, C. C. Gilbert (eds.), Elwyn Simons: A Search for Origins. Ó Springer 2008

181

182

D. T. Rasmussen et al.

(Kappelman et al., 1992; Seiffert, 2006). The Simons influence on the Early Tertiary is also manifested by the enlarging ripples of research activity by his students and colleagues at the ever-growing number of other localities found on the continent. Several veterans of the Fayum field crews have gone on to make notable contributions to the early Tertiary of African nations other than Egypt (e.g., Court and Hartenberger, 1992; Godinot, 1994; Kappelman et al., 2003; Stevens et al., 2005, 2006; 2008). While Simons himself has not strayed from Egypt (if one considers only the Early Tertiary of Africa), at one point he had planned to do so. He organized an expedition to Libya in the late 1960’s when the smooth continuation of his Egypt project was disrupted by war in the region. While Simons’ Libya project never came to fruition, stories of the aborted effort told around the Fayum field camp in the 1980’s intrigued graduate students at the time. This paper describes a new field project in Libya that represents the continuation, after a 36 year hiatus, of paleontological exploration at one of the most important early Tertiary sites of Libya: a long escarpment deep in the Sahara called Dor al-Talha.

History While Simons was initiating his museum work on Fayum mammals in the 1950s and long before he took to the field in the early 1960s, French geologists exploring for petroleum resources in the deserts of Libya reported the occurrence of Tertiary vertebrates at a few locations (Bellair et al., 1954). The French paleontologist Camille Arambourg provided a preliminary description of these geological outcrops and the fossil mammals they yielded (Arambourg and Magnier, 1961; Arambourg, 1963). Most importantly, Arambourg showed that a few archaic proboscideans and hyracoids recovered from Libya were nearly identical to ones from the Fayum that had been discovered in the early part of the century (Andrews, 1906; Osborn, 1908; Schlosser, 1911). These mammals could be found at two Libyan localities. One of these was near the oasis of Zella, the potential of which was limited, Arambourg complained, by a lack of appropriate exposure (Arambourg and Magnier, 1961; Savage, 1971; Fejfar, 1987). The other locality was a much more extensive escarpment in the desert to the south called Dor al-Talha, ‘‘home of the acacias’’.* * The name Dor al-Talha was first applied to the escarpment in a geological context by Bellair et al. (1954). For some reason, Arambourg coined his own term, ‘‘Gebel Coquin’’ for the same escarpment. Savage (1971) rejected that term as ‘‘singularly inappropriate’’ in favor of the original Dor al-Talha. Savage’s student A. W. R. Wight used the spelling Dur at-Talha. Savage reports that the term means ‘‘long escarpment’’ but, in Arabic, it actually means ‘‘home or place of the acacia trees.’’ There are no acacia trees evident there now, and it is unknown whether the name refers to real acacia stands now gone, or was an allusion to the numerous fossil tree trunks evident in the area.

Return to Dor al-Talha

183

Shortly thereafter, the British paleontologist Robert J. G. Savage of the University of Bristol initiated a series of field projects in Libya. Savage and his students packed their equipment into vehicles and took a drive-and-ferry marathon from Great Britain through France, Spain, Morocco, Algeria, Tunisia, Tripoli, and finally out to eastern Libya. Savage’s primary focus was on the rich Miocene deposits of Jebel Zelten (Arambourg, 1961; Savage, 1971; Gaziry, 1987). But Savage and his student A. W. R. Wight also spent several weeks in 1968 and 1969 working from a camp set up at the escarpment of Dor al-Talha to characterize the geology of the scarp and to collect fossil mammals (Savage, 1969, 1971; Wight, 1980). In the few publications resulting from these trips, Savage and Wight presented taxonomic lists of fossils recovered, and a very good outline of the local stratigraphy. No supporting photos of the fossils or of the geological outcrops were published at the time. Years later, two of the important mammal specimens from Dor al-Talha were illustrated as part of subsequent museum research projects (Tassy, 1981; Court, 1995). In Egypt, where Simons had established his Fayum field effort in 1961, the Six-Day War of the summer of 1967 led to restrictions being placed on desert travel in the country by foreigners and Egyptians alike. Simons tried to run an Egyptian field project in 1968, but when that faltered, he looked to Libya as a potential new research area. He dispatched a small crew to Libya in the late summer of 1969 that consisted of Prithijit Chatrath, Thomas Bown, and Tony Gaston. The trio arrived in Libya after a drive from India to Italy and a ferry crossing from there to Tripoli. They were staying in a Tripoli hotel and preparing to take to the field when the Libyan Revolution occurred on September 1st, 1969, which led to the abandonment of the project (T. M. Bown, P. S. Chatrath, personal communication). The Savage expeditions of 1968 and 1969 thus constituted the end of major research activity on Early Tertiary vertebrates of Libya for many years. The most important new addition to the study of Libyan early Tertiary mammals since that time has been the description of beautifully articulated Oligocene hyracoid skeletons found at Jebel al-Hasawnah by a private collector (Thomas et al., 2004). This site is far to the west of Dor al-Talha and the Sirt Basin in an area where the Oligocene beds are associated with older exposures of Early Tertiary and Cretaceous rocks. In the meantime, the geological sciences in Libya developed and grew, with an obvious focus being the country’s rich petroleum resources and their associated sedimentary contexts (e.g., Wennekers et al., 1996; Ahlbrandt, 2001). Knowledge of Early Tertiary sediments, their distribution, precise age and sedimentological characteristics have been well elucidated for a number of areas, primarily in the Sirt Basin (Selley, 1969, 1997; Gumati and Kanes, 1985; Salem et al., 1996). Ongoing basic research has led to great gains in understanding Libyan stratigraphy, micropaleontology, and other areas related to the Early Tertiary history of the country. Following political changes that developed in 2004, the four authors of this paper began collaborating on plans to launch new work on vertebrate fossils in

184


the Early Tertiary of Libya. The four included two American vertebrate paleontologists and two Libyan geologists who shared interests in the geological history of Libya and Africa. A trip was planned that consisted of two parts: (1) a look at some Cretaceous exposures from which dinosaurs had been reported (Smith et al., in press), and (2) a look at the early Tertiary sites worked by Arambourg and Savage. This preliminary reconnaissance trip under the auspices of the Petroleum Research Centre (PRC) of Tripoli was completed Aug. 7th–28th, 2005, and the preliminary results of this trip are presented here. Funding was by the PRC and by Washington University, St. Louis.

The Early Tertiary of Libya Sedimentary deposits of early Tertiary age are exposed primarily in the northeastern part of the country. Arambourg (1963) had included the Libyan sites and those of the Fayum together under a term ‘‘The Nilotic-Saharian Zone’’, reflecting that they accumulated under in a common geological context. The northern margin of Africa during the early Tertiary was tectonically fairly quiet (with a few exceptions outlined below). River systems flowing to the Tethys Sea generated aggrading fluvial deposits as the rivers and the load of sediment they carried leveled off on a broad African coastal plane (e.g., Bown and Kraus, 1988). Kortlandt (1980) and others have erroneously attributed the Fayum deposits, only 60 km from the Nile River, to the action of a ‘‘proto-Nile,’’ an idea criticized by geologists working in the Fayum (e.g., Bown et al., 1982). The extension of fluvial deposits similar to those of the Fayum westwards into Libya is one of several lines of evidence that the depositional context was not generated by one massive river originating deep in the African interior, but rather by a series of streams draining what was, at the time, tropical forests under a high rainfall regime. Suggestions that evaporites found in some early Tertiary sediments of North Africa indicate an arid climate at the time of deposition ignore the fact that gypsum and other evaporites can develop diagenetically (Bain, 1990). All inferences about the North African climate during the early Tertiary that are based on the communities of fossil plants, birds, and mammals, indicate lush tropical conditions (Bown et al., 1982; Olson and Rasmussen, 1986; Wing, personal communication). The watershed patterns that developed along the Tethyan floodplain of early Tertiary Africa are not analogous or ancestral to the Nile. The shoreline of Africa during the early Tertiary was geographically positioned further to the south than it is today. Most of the Eocene beds of northeastern Africa are marine, but several deposits represent nearshore or terrestrial accumulations, particularly westwards towards the Saharan Atlas (e.g., Mahboubi et al., 1986). The Eocene was a time of marine transgression and regression across the region, with marine conditions predominating in


185

Egypt and, apparently, in Libya. Terrestrial lenses of Eocene age (representing temporary or local regressions) embedded within broader marine deposits have been found in Egypt and Oman (e.g., Seiffert et al., 2005; Thomas et al., 1999). The Eocene-Oligocene transition was marked by a worldwide regressive event that should be identifiable in terrestrial sequences by an erosional unconformity (Bown and Kraus, 1987; Kappelman et al., 1992; Seiffert, 2006), and in theory at least, by a transition in other places from nearshore marine to terrestrial conditions. A relatively uninterrupted stratigraphic column at any one geographic spot should show, from the Paleocene through the Oligocene, a transition from offshore marine, to nearshore marine and estuarine conditions, and finally to terrestrial environments. The precise pattern of marine, nearshore and terrestrial sediments of early Tertiary age across northern Egypt and Libya were presumably influenced by local permutations in river flow, surface topography, and subtle tectonic action. Analysis of drill cores from the rich petroleum fields of northeastern Libya provides just such a test of these general geological models. Cores from the Sirt Basin there confirm a general marine to terrestrial transition as one progresses through the Early Tertiary, and provide quite a bit of detail on the local stratigraphy, lithology and dating (e.g., Salem, 1996; Ahlbrandt, 2001). A distinctive feature of Libyan geology, when compared to that of Egypt, is that there was small-scale but significant rifting from the Cretaceous into the Paleocene and Eocene (Gumati and Kanes, 1985). There were three primary grabens of this age range formed in what is now terrestrial Libya. The two eastern ones are covered by Quaternary deposits, but the westernmost one, the Hun Graben, is subareally exposed. Field study by Libyan geologists (Geological Map of Libya, 1985) identified the rock contained within the graben as primarily Eocene marine calcareous muds, but with a variety of other sedimentary types, while the graben walls are Paleocene and Cretaceous marine sediments uncapped by younger sediment. We visited the Hun Graben to examine some of the local facies; the sedimentary rock we saw in our brief stop there was consistent with the previous, more detailed mapping work in revealing no evidence of terrestrial or nearshore conditions. The problem of finding local or extensive terrestrial lenses within the Libyan Tertiary series ultimately comes down to surface prospecting for fossils. Much of the Early Tertiary deposits are covered by aeolian sand, or are exposed in very low relief in the form of great expansive desert flats crusted by serir, or desert pavement. Prospecting for fossil vertebrates in these conditions ranges from impossible to difficult. Savage reported a spot in which numerous fossil sirenians were weathering on the surface in the middle of these expansive Tertiary deposits (Savage, 1971). Local, low-relief escarpments exist that expose shallow stratigraphic sections; the outcrops that yielded the vertebrates of Zella represent such an occurrence (Arambourg and Magnier, 1961; Fejfar, 1987). We spent a single day surface prospecting outcrops in the Zella region, without being able to pinpoint Arambourg’s precise locality. While we encountered no terrestrial sediments or vertebrates, we were able to confirm that the local

186


stratigraphic column was fairly complex, comprising a variety of marine rocks, including limestones, calcareous muds, sandstones, and mudstones, including beds lacking fossils and others with a mash of marine invertebrates. Prospecting the flat Paleogene exposures of Libya in the future will presumably rely on intensive survey of outcrops of this kind. For the most part, the extensive early Tertiary of Libya has yielded little to paleontologists interested in terrestrial vertebrates, with two impressive exceptions. The first is the articulated hyracoids and frogs of Jebel al Hasawnah (Thomas et al., 2004), the second is Dor al-Talha. The Paleogene beds of Libya have a gentle dip to the north. The southernmost rim of this vast tilted bank of Early Tertiary sediment lies at the south-facing escarpment of Dor al-Talha, which stretches along an east-west axis for over 100 km. This is where Bellair et al. (1954), Arambourg and Magnier (1961), Savage (1969) and Wight (1980) found fossil vertebrates of estuarine and terrestrial origin.

Dor al-Talha Accessing the escarpment involved a 400 km drive on sandy desert tracks from the Zella oasis, curving around the eastern margin of the al-Haruj Basalts, and arriving on the top of the scarp. The al-Haruj basalts represent six or seven flows ranging in age from late Pliocene to late Pleistocene or early Holocene (Klitsch, 1967, Busrewil et al., 1996). Much of the drive looping around to the east of al-Haruj is over Quaternary wind-blown sand and early Tertiary sediment, but the latter is usually poorly exposed. The broken escarpment stands north of a great depression filled with feshfesh, extremely fine-grained aeolian accumulations. The feshfesh basin represents a sea of dry loess-like powder, covering at least 8500 km2, which Savage (1971) described as being ‘‘very difficult to traverse by car’’ The escarpment is shown in Figs. 1–3. The scarp is generated by erosive action on a resistant sandstone deposit that forms the escarpment rim, rich in fossil wood, which overlies finer-grained and softer mudstones, siltstones, and sandstone lenses. The vertebrates come from the finer-grained rocks which, by virtue of the erosional resistance of the rimming sandstones, are exposed as cliffs and bluffs (Fig. 1). In our trip, we contacted the scarp at a point not well sampled by Savage and Wight, and so our work represents an independent assessment of the geology and fossils. The 13 localities we found were new, but the results we obtained were consistent with those of Wight (1980). Wight divided the sediments of Dor al-Talha into three members. The lowest of these members—which at its base is overlapped by the feshfesh to the south— is called the Evaporite Unit (Fig. 2). Wight interpreted this as a marine deposit based on the limited mammalian fauna of moeritheres and barytheres. The preservation of vertebrate bones at this level is, in our limited experience, very


187

Fig. 1 View from the top of the Dor al-Talha escarpment looking south. The yellow-brown sandstones of the foreground erode as dark, broken cliffs (visible at background right), with broad wadis washing through softer, underlying sediment towards the feshfesh basin at the distant horizon

poor (Fig. 4). The bones are soft, fractured, and chalky. The abundant evaporites seem to be diagenetic, and not related to depositional conditions. The next oldest stratigraphic unit of Wight is the Idam Unit (Fig. 3). This unit consists of fine to medium-grained clastics. While not uniformly fossiliferous, local spots produce vertebrate fossils in notable concentrations. The Idam Unit was the primary producer of the fossil mammals listed by Savage. We found a wealth of vertebrates there. Our finds suggest that environments of deposition were varied, and contained at least some terrestrial contexts. Some of the Idam Unit localities consisted of broken and unassociated fragments that represent a mixed assemblage of aquatic and terrestrial vertebrates. For example, locality DT-01 (Fig. 3) includes broken and dissociated specimens of sawfish, catfish, gar, turtles, crocodilians (including Tomistoma), and the mammals Moeritherium and indeterminate members of Hyracoidea. In contrast, another PRC locality, DT-13 (found in the last hour of dusk on our last day in the field by S. T. and M. M. A.), was characterized by extremely wellmineralized fossils layed out as loosely associated skeletons in fine-grained clasts. The vertebrate taxa included silurid catfish, the crocodilian Tomistoma (Fig. 5), and the mammal Moeritherium. These two localities attest to the

188


Fig. 2 Sedimentary rock of the Evaporite Unit eroding as rounded bluffs and soft slopes (kneeling J. B. S. as a scale bar in center left). A butte of the overlying Idam Unit is seen rising in the center background

potential diversity of environmental and taphonomic conditions among sites at Dor al-Talha. The uppermost stratigraphic unit of Wight was reported to be devoid of vertebrates but it did contain fossil wood. We spent no time prospecting for vertebrates here, given our limited schedule, and our paleontological observations are basically limited to the fact that, in local places, we had to drive carefully to avoid fossil tree trunks distributed on the landscape. No vertebrates were seen in this unit. Paleoenvironmental reconstructions of the Dor al-Talha stratigraphic units are particularly important. The Evaporite Unit seems to be primarily marine, albeit nearshore marine, given the prevalence of Moeritherium, Barytherium, and some freshwater or estuarine fish and crocodilian groups (Wight, 1980). The uppermost unit is full of fossil trees, some quite large, indicating stable terrestrial conditions. The Idam Unit contains non-aquatic vertebrates like Arsinoitherium, Palaeomastodon and Hyracoidea, suggesting that at certain times and places, the accumulations are derived from terrestrial conditions. However, the Idam Unit also contained many aquatic, and in some cases, marine vertebrates as well; for example, we collected in this unit a vertebra of Gigantophis, a huge snake believed to be marine (Andrews, 1906). The interpretation that local terrestrial conditions did exist is supported by massive tree trunks in the Idam Unit (Fig. 6); further analysis of the Idam Unit’s fossil forest


189

Fig. 3 Typical appearance of the Idam Unit, a highly fossiliferous unit containing a diversity of rock types and fossils. Locality PRC DT-01 consists of the slope in the left foreground below the bench-forming light sandstone (M. M. A. prospects for fossils on the right end of the outcrop)

Fig. 4 A complete but badly deteriorated humerus of Barytherium from locality PRC DT-11, in the Evaporite Unit. The proximal end is to the left, the deltoid crest is visible spiraling around the shaft at center, and the broad distal end is on the right. The bone is chalky, and badly fissured from weathering

190


Fig. 5 Fossil remains of the long-nosed crocodilian Tomistoma, a genus currently extant in Southeast Asia, from the Idam Unit locality PRC DT-13. These fossils are heavily mineralized and well preserved, in contrast to those from the Evaporite Unit. The individual pieces illustrated here represent bones of a single individual (including cranial fragments, scutes, and the upper and lower jaw seen in the foreground) that were scattered on the surface over a few square meters (they have been arranged close together for the photo). Remains of several other individuals of Tomistoma, large fish, and Moeritherium, were also found at this site

localities will be required to confirm that these are in situ forests, rather than transported, floating wood (cf. Bown et al., 1982).

Fossil Mammals We concluded the fieldwork three weeks before the Simons conference, and have not analyzed the mammals and other vertebrates we collected in any detail. We can report that the fauna we encountered in a couple days of intensive field collection matched well taxonomically with the fauna reported by Savage (1971) and Wight (1980). The most common mammals found in the old pioneering trips to Dor al-Talha were quickly duplicated by us: we found remains of the Early Tertiary proboscideans Moeritherium, Barytherium and Palaeomastodon, of the embrithopod Arsinoitherium, and bone fragments of smaller, indeterminate mammals, most likely hyracoids. The most abundant fossil vertebrates were those of fish, particularly silurid catfish, lungfish, sawfish and gars. Among reptiles, remains of the long-nosed crocodilian Tomistoma were particulary common.


191

Fig. 6 Large fossil tree trunks exposed at locality DT-04 of the Idam Unit (J. B. S. serves as scale). Vertebrates were not found at this locality, but it occurs at nearly the same stratigraphic level as DT-13 and other vertebrate-bearing sites. This view looking south provides another view of landscapes within the Idam Unit

Moeritherium is a primitive proboscidean with bunodont teeth and short, robust chisel-like tusks (Tassy, 1981). It has been recovered at several Early Tertiary sites in Africa, and the depositional contexts of these finds suggest it was amphibious. Based on a specimen recovered by the early Simons expeditions to the Fayum, the body shape also supports this interpretation: Moeritherium was a heavy, long-bodied, short-legged form. We recovered several postcranial and dental specimens of Moeritherium from the Idam Unit, including a well-preserved and lightly worn maxillary dentition that will contribute to the investigation of species-level taxonomy in this genus. In addition, we found an eroded cranium from the Evaporite Unit that is comparable in preservation to the important Arambourg specimen described by Tassy (1981). Barytherium graves is a very large proboscidean with specialized bilophodont teeth, closely resembling much later deinotheres in that one respect, and differing dramatically from bunodont Moeritherium and Palaeomastodon. B. graves was a common component of the early collections from Dor al-Talha, including a partial postcranial skeleton, but the material recovered by Arambourg and Savage has never been fully described. Barytherium has not been found outside Dor al-Talha except for a few, poor specimens from Eocene levels of the Fayum (Andrews, 1906; Simons, 1968); this genus remains a Libyan specialty item. We found several dental specimens of Barytherium during our reconnaissance trip.

192


Wight (1980) suggested that a smaller species of Barytherium was present at Dor al-Talha but did not describe it formally. Later, a lower jaw representing this taxon was described as a new species of the very primitive proboscidean Numidotherium (Mahboubi et al., 1984; Court, 1995). Whether this really represents a species of Barytherium, Numidotherium, or something new, is a question that deserves further study, and it will probably require the recovery of new material. We found one molar specimen of the smaller bilophodont proboscidean. The primitive proboscideans of Africa are taxa of great interest to evolutionary biologists (e.g., Gheerbrant et al., 2002). Palaeomastodon is a proboscidean well known from the Early Tertiary of Africa, and is best characterized to date from the Fayum, Egypt, and Chilga, Ethiopia (Tobien, 1971; El-Kashab, 1979; Sanders et al., 2004). Unlike Moeritherium, Barytherium, and Numidotherium—which represent distant outgroups to the lineages that gave rise to Late Tertiary mastodons, deinotheres, elephants, and their kin—Palaeomastodon is considered to be an early member of the elephantiform stock (Tassy, 1994). It was an animal with bunodont but linearly seriated tooth cusps that provide an obvious ancestral condition for gomphotheres and deinotheres (Sanders et al., 2004). The anterior teeth were elongated into tusks, spatulate in shape, and appressed at the midline, unlike those of modern elephants. We recovered a few dental fragments of Palaeomastodon. Arsinoitherium is a massive, horned mammal with bizarre high-crowned teeth that is known only from the Early Tertiary of a few African sites (Court, 1992a, 1992b, 1993). It is best known from latest Eocene and early Oligocene levels of the Fayum (Andrews, 1906; El-Kashab, 1977; Tanner, 1978), and from the Late Oligocene of Chilga, Ethiopia (Sanders et al., 2004). Postcranial remains of Arsinoitherium have been reported from the Fayum (Andrews, 1906; Court, 1993). At Dor al-Talha, we recovered one specimen that consists of an associated complete tibia and fibula, very well preserved, from the Idam Unit. The specimen matches very well with a tibia of Arsinoitherium described by Andrews (1906). The tibia and fibula of Barytherium, a similarly sized animal, remain undescribed, and so comparisons to that taxon are impossible. The discovery of well-preserved, complete leg bones of Arsinoitherium in the Idam Unit is of interest because Arsinoitherium, in contrast to Moeritherium and possibly Barytherium, was indisputably an animal of terrestrial environments (Court, 1993; Kappelman et al., 2003). Wight reported a very few number of specimens of Arsinoitherium from Dor al-Talha. In addition to the large probosideans and embrithopods, we recovered several fragments representing smaller mammals, probably hyracoids, pending further study. Hyracoids were a dominant order of terrestrial mammals in the Early Tertiary of Africa, both in terms of abundance and diversity (Rasmussen, 1989; Rasmussen and Gutierrez, in press). We collected an occipital bone with its condyles, an innominate with the acetabulum, and several mammalian vertebral fragments that all fall within the size range of hyracoids ranging in body mass between Thyrohyrax and Pachyhyrax. These specimens, collected in only a couple of days on the outcrops at Dor al-Talha, suggest that there is potential


193

to find additional mammalian taxa. The obvious similarities to the Fayum fauna suggest the possibility of finding primates (Simons, 1987, 1990, 1995, 1997, 2001).

Conclusions The stratigraphic work conducted by A. W. R. Wight in the late 1960s, during short trips to Dor al-Talha, was very useful to us, and it proved to be reliable and accurate in a general sense (Wight, 1980). The abundance of fossil vertebrates at the escarpment is confirmed. The Evaporite Unit appears to be primarily marine. The poor preservation of fossils there and the abundant evaporites are probably diagnetic in nature, not necessarily reflecting an arid environment. The Idam Unit is particularly fossiliferous and holds much promise for further work on the Libyan mammal communities of the Early Tertiary. The fossils are well preserved, and consist of both terrestrial and semiaquatic taxa. The Dor al-Talha faunal community, as currently construed based on very preliminary sampling, may represent one of the best assemblages of basal proboscideans and embrithopods known from Africa. The diversity among Dor al-Talha sites and the great geographic extent of the exposures suggests that future work on fossils, dating, and ecological context will continue to illuminate evolutionary and paleoenvironmental events in the northern part of the African-Arabian continent during the Early Tertiary.

References Ahlbrandt, T. S. (2001). The Sirte Basin Province of Libya – Sirte-Zelten total petroleum system. U. S. Geological Survey Bulletin 2202-F: 1–29. Andrews, C. W. (1906). A Descriptive Catalogue of the Tertiary Vertebrata of the Fayum, Egypt. British Museum (Natural History), London, 324 pages, 26 plates. Arambourg, C. (1961). Note pre´liminaire sur quelques Verte´bre´s nouveaux du Burdigalien de Libye. Comptes Rendus Sommaire des Seances de la Socie´te´ Geólogique de France 4: 107–109. Arambourg, C. (1963). Continental vertebrate faunas of the Tertiary of North Africa. In: Howell, F. C., and Bourliere, F. (eds.), African Ecology and Human Evolution. Aldine, Chicago, pp. 55–60. Arambourg, C., and Magnier, P. (1961). Gisements de verte´bre´s dans le bassin tertaire de Syrte (Libie). Comptes Rendus Hebdomadaires des Seánces de l’Academie de Sciences 252: 1181–1183. Bain, R. J. (1990). Diagenetic, nonevaporative origin for gypsum. Geology 18, 447–450. Bellair, P., Freulon, J., and Lefranc, J. (1954). Dećouverte d’une formation a´ verte´bre´s et ve´ge´taux d’aˆge tertiaire au bord occidental du de´sert libyque (Sahara occidental). C. R. Acad. Sci. Paris 239: 1822–1824. Bown, T. M., and Kraus M. J. (1988). Geology and paleoenvironment of the Oligocene Jebel Qatrani Formation and adjacent rocks, Fayum Depression, Egypt. U. S. Geol. Surv. Prof. Paper 1452: 1–60.

194


Bown, T. M., Kraus, M. J., Wing, S. L., Fleagle, J. G., Tiffney, B. H., Simons, E. L., and Vondra, C. F. (1982). The Fayum primate forest revisited. J. Hum. Evol. 11: 603–632. Busrewil, M. T., Mriheel, I. Y., and Al-Fasatwi, T. A. (1996). Volcanism, tectonism, and hydrocarbon potential of parts of Al Haruj area, SW Sirt Basin, Libya. In: Salem, M. J., Mouzughi, A. J., and Hammuda, O. S. (eds.), The Geology of Sirt Basin, Volume 3. Elsevier, Amsterdam, pp. 317–329. Court, N. (1992a). The skull of Arsinoitherium (Mammalia, Embrithopoda) and the higher order interrelationships of ungulates. Palaeovertebrata 22, 1–43. Court, N. (1992b). A unique form of dental bilophodonty and a functional interpretation of peculiarities in the masticatory system of Arsinoitherium (Mammalia, Embrithopoda). Hist. Biol. 6: 91–111. Court, N. (1993). Morphology and functional anatomy of the postcranial skeleton in Arsinoitherium (Mammalia, Embrithopoda). Palaeontolographica Abhandlungen A 226: 125–169. Court, N. (1995). A new species of Numidotherium (Mammalia: Proboscidea) from the Eocene of Libya and the early phylogey of the Proboscidea. J. Vertebr. Paleontol. 15: 650–671. Court, N., and Hartenberger, J.-L. (1992). A new species of the hyracoid mammal Titanohyrax from the Eocene of Tunisia. Palaeontology 35: 309–317. El-Kashab, B. (1977). Approach on genus Arsinoitherium and the diagnosis of its closely related sympatric fossil species, in Lower Oligocene of Fayum Province Egypt. The Geological Survey of Egypt and Mining Authority, Cairo, Paper No. 62: 29–39. El-Kashab, B. (1979). A brief account of Egyptian Paleogene Proboscidea. Annals of the Geological Survey of Egypt 9: 245–260. El-Kashab, B., Simons, E. L., and Fleagle, J. G. (1983). Annotated bibliography of Egyptian vertebrate fossils up to the end of 1980. Geological Survey of Egypt and Mining Authority, Cairo, Paper No. 65: 1–111. Fejfar, O. (1987). Oligocene rodents from Zallah Oasis, Libya. Mu¨nchner Geowissenschaften Abhandlungen A 10: 265–268. Gaziry, A. W. (1987). New mammals from the Jabal Zaltan site, Libya. Senckenbergiana lethaea 68: 69–89. Geological Map of Libya (1985). First Edition. Geological Researches and Mining Department, Industrial Research Center, Tripoli. Gheerbrant, E., Sudre, J., Cappetta, H., Iarochene, M., Amaghzaz, M., and Bouya, B. (2002). A new large mammal from the Ypresian of Morocco: Evidence of surprising diversity of early proboscideans. Acta Palaeontol. Pol. 47: 493–506. Gingerich, P. D. (1992). Marine mammals (Cetacea and Sirenia) from the Eocene of Gebel Mokattam and Fayum, Egypt: stratigraphy, age, and paleoenvironments. University of Michigan, Papers on Paleontology 30, 1–84. Gingerich, P. D. (this volume). Early evolution of whales: A century of research in Egypt. In: Fleagle, J. G. (ed.), Elwyn L. Simons: Mapping the Progress of Primate Evolution. Plenum Press, New York. Godinot, M. (1994). Early North African primates and their significance for the origin of Simiiformes (= Anthropoidea). In: Fleagle, J. G., and Kay, R. F. (eds.), Anthropoid Origins. Plenum Press, New York, pp 235–295. Gumati, Y. D., and Kanes, W. H. (1985). Early Tertiary subsidence and sedimentary facies – northern Sirte Basin, Libya. Am. Assoc. Petr. Geol. B. 69: 39–52. Kappelman, J., Simons, E. L., and Swisher, C. C., III (1992). New age determinations for the Eocene-Oligocene boundary sediments in the Fayum depression, northern Egypt. J. Geol. 100: 647–667. Kappelman, J., Rasmussen, T., Sanders, W., Feseha, M., Bown, T. M., Copeland, P., Crabaugh, J., Fleagle, J., Glantz, M., Gordon. A., Jacobs, B., Maga, M., Muldoon, K., Pan, A., Pyne, L., Richmond, B., Ryan, T., Seiffert, E., Sen, S., Todd, L., Wiemann, M. C.,


195

and Winkler, A. (2003). Oligocene mammals from Ethiopia and faunal exchange between Afro-Arabia and Eurasia. Nature 426: 549–552. Klitsch, E. (1967). Der Basaltvulkanismus des Jabal Haruj, Ostfezzan/ Libyen. Geol. Rdsch. 57: 585–601. Kortlandt, A. (1980). The Fayum primate forest: Did it exist? J. Hum. Evol. 9: 277–297. Mahboubi, M., Ameur, R., Crochet, J. Y., and Jaeger, J.-J. (1984). Earliest known proboscidean from the early Eocene of north-west Africa. Nature 308: 543–544. Mahboubi, M., Ameur, R., Chrochet, J. Y., and Jaeger, J.-J. (1986). El Kohol (Saharan Atlas, Algeria), a new Eocene mammal locality in northwestern Africa: stratigraphic, phylogenetic and paleobiogeographical data. Palaeontographica Abteilung A, 192, 15–49. Miller, E. R. (1999). Faunal correlation of Wadi Moghara, Egypt: Implications for the age of Prohylobates tandyi. J. Hum. Evol. 36: 519–533. Olson, S. L., and Rasmussen, D. T. (1986). The paleoenvironment of the earliest anthropoids: new evidence from the Oligocene avifauna of Egypt. Science 233: 1202–1204. Osborn, H. F. (1908). New fossil mammals from the Fayum Oligocene, Egypt. B. Am. Mus. Nat. Hist. 24: 265–272. Rasmussen, D. T. (1989). The evolution of the Hyracoidea: a review of the fossil evidence. In: Prothero, D. R., and Schoch, R. M. (eds.), The Evolution of Perissodactyls. Oxford University Press, New York, pp. 57–78. Rasmussen, D. T., Bown, T. M., Simons, E. L. (1992). The Eocene-Oligocene transition in continental Africa. In: Prothero, D. R., and Berggren, W. A. (eds), Eocene-Oligocene Climatic and Biotic Evolution. Princeton Univ., Princeton, New Jersey, pp. 548–566. Salem, M. J., El-Hawat, A. S., and Sbeta, A. M. (1996). The Geology of the Sirt Basin, Volume 1. Elsevier, Amsterdam. Sanders, W. J., Kappelman, J., Rasmussen, D. T. (2004). New large-bodied mammals from the late Oligocene site of Chilga, Ethiopia. Acta Palaeontol. Pol. 49: 365–392. Savage, R. J. G. (1969). Early Tertiary mammal locality in southern Libya. P. Geol. Soc. London 1657: 167–171. Savage, R. J. G. (1971). Review of the fossil mammals of Libya. In: Gray, C. (ed.), Symposium on the Geology of Libya. University of Libya, Tripoli, pp. 215–226. Schlosser, M. (1911). Beitrage zur kentniss der Oligozanen Landsaugetiere aus dem Fayum, Egypt. Beitr. Palaeont. Geol. Ost. Ung., Wien 24: 51–167. Seiffert, E. R. (2006). Revised age estimates for the later Paleogene mammal faunas of Egypt and Oman. P. Natl. Acad. Sci. USA 103: 5000–5005. Seiffert, E. R., Simons, E. L., and Attia, Y. (2003). Fossil evidence for an ancient divergence of lorises and galagos. Nature 422: 421–424. Seiffert, E. R., Simons, E. L., Clyde, W. C., Rossie, J. B., Attia, Y., Bown, T. M., Chatrath, P. S., and Mathison, M. E. (2005). Basal anthropoids from Egypt and the antiquity of Africa’s higher primate radiations. Science 310: 300–304. Seiffert, E. R. (2008). Geology, paleoenvironment, and age of Birket Qarun Locality 2 (BQ-2), Fayum Depression, Egypt. In: Fleagle, J. G. and Gilbert, C.C. (eds.), Elwyn Simons: A Search for Origins. Springer, New York, pp.71–86. Selley, R. C. (1969). Nearshore marine and continental sediments of the Sirte Basin, Libya. Quarterly Journal of the Geological Society of London 124: 419–460. Selley, R. C. (1997). The Sirte Basin of Libya. In: Selley, R. C. (ed.), The Sedimentary Basins of the World, Volume 3. Elsevier, Amsterdam, pp. 27–37. Simons, E. L. (1968). Early Cenozoic mammalian faunas, Fayum Province, Egypt, Part I, African Oligocene mammals: introduction, history of study, and faunal succession. Peabody Museum of Natural History, Yale University, Bulletin 28:1–21. Simons, E. L. (1987). New faces of Aegyptopithecus from the Oligocene of Egypt. J. Hum. Evol. 16: 273–289. Simons, E. L. (1990). Discovery of the oldest known anthropoidean skull from the Paleogene of Egypt. Science 247: 1521–1612.

196


Simons, E. L. (1995). Crania of Apidium: primitive anthropoidean (Primates, Parapithecidae) from the Egyptian Oligocene. Am. Mus. Nov. 3124: 1–10. Simons, E. L. (1997). Preliminary description of the cranium of Proteopithecus sylviae, an Egyptian Late Eocene anthropoidea primate. P. Natl. Acad. Sci. USA 94: 14970–14975. Simons, E. L. (2001). The cranium of Parapithecus grangeri, an Egyptian Oligocene anthropoidean primate. P. Natl. Acad. Sci. USA, 98: 7892–7897. Simons, E. L., and Rasmussen, D. T. (1995). A whole new world of ancestors: Eocene anthropoideans from Africa. Evol. Anthropol. 3: 128–139. Smith, J. B., Askar, A. S., Bergig, K. A., Tshakreen, S. O., Abugares, M. M., Sliman, O., Lamanna, M. C., and Rasmussen, D. T. (in press). An abelisauroid theropod dinosaur from the Early Cretaceous of Libya. Naturwissenschaften 00, 000–000. Stevens, N., O’Conner, P. M., Gottfried, M. D., Roberts, E. M., and Ngasala, S. (2005). An anthropoid primate humerus from the Rukwa Rift Basin, Paleogene of southwestern Tanzania. J. Vertebr. Paleontol. 25: 986–989. Stevens, N., O’Conner, P. M., Gottfried, M. D., Roberts, E. M., Ngasala, S., and Dawson, M. R. (2006). Metaphiomys (Rodentia: Phiomyidae) from the Paleogene of southwestern Tanzania. J. Paleontol. 80: 407–410. Stevens, N. J., Gottfried, M. D., Roberts, Saidi Kapilima, E. M., Ngasala, and O’Conner, P. M. (2008). Paleontological Exploration in Africa: A View from the Rukwa Rift Basin of Tanzania. In: Fleagle, J. G. and Gilbert, C.C. (eds.), Elwyn Simons: A Search for Origins. Springer, New York, pp.159–180. Tanner, L. G. (1978). Embrithopoda. In: Maglio, V. J., and Cooke, H. B. S. (eds.), Evolution of African Mammals. Harvard University Press, Cambridge, Massachusetts, pp. 279–283. Tassy, P. (1981). Le craˆne de Moeritherium (Proboscidea, Mammalia) de l’Eóce`ne de Dor el Talha (Libye) et le proble`me de la classification phylogeńe´tique du genre dans les Tethytheria McKenna, 1975. Bull. Mus. Natn. Hist. Nat., Paris, 4e se´r., 3, section C., no 1, 87–147. Tassy, P. (1994). Origin and differentiation of the Elephantiformes (Proboscidea, Mammalia). Verhandlungen Naturwissenschaftlichen Vereins in Hamburg 34, 73–94. Thomas, H., Roger, R., Sen, S., Pickford, M., Gheerbrant, E., Al-Sulaimani, Z., and Al-Busaidi, S. (1999). Oligocene and Miocene terrestrial vertebrates in the southern Arabian Peninsula (Sultanate of Oman) and their geodynamic and palaeogeographic settings. In: Whybrow, P. J., and Hill, A. (eds.) Fossil Vertebrates of Arabia. Yale Univ., New Haven, pp. 430–442. Thomas, E., Gheerbrant, E., and Pacaud, J. M. (2004). Dećouverte de squelettes subcomplets de mammife`res dans le Paleóge`ne d’Afrique (Libye). C. R. Palevol 3: 209–218. Tobien, H. (1971). Moeritherium, Palaeomastodon, Phiomia aus dem Palaögen Nordafricas und die Abstammung der Mastodonten (Proboscidea, Mammalia). Mitteilungen aus dem Geolischen Institut der Technischen Universita¨t Hannover 10, 141–163. Wennekers, J. H. N., Wallace, F. K., and Abugares, Y. I. (1996). The geology and hydrocarbons of the Sirt Basin: A synopsis. In: Salem, M. J., El-Hawat, A. S., and Sbeta, A. M. (eds.), The Geology of the Sirt Basin, Volume 1. Elsevier, Amsterdam, pp. 3–56. Wight, A. W. R. (1980). Palaeogene vertebrate fauna and regressive sediments of Dur at Talha, southern Sirt Basin, Libya. In: Salem, M. J., and Busrewil, M. T. (eds.), The Geology of Libya, Volume 1. Academic Press, London, pp. 309–325. Wing, S. L., and Tiffney, B. H. (1982). A paleotropical flora from the Oligocene Jebel Qatrani Formation of northern Egypt: A preliminary report. Miscellaneous Series of the Botanical Society of America 162, 67.