Birket Qarun Research Articles

Multiproxy faunal analysis of the middle – upper Eocene deposits in the Fayum area, Egypt: Insights into sequence stratigraphy, trophic conditions, and oxygenation

The Eocene epoch experienced significant fluctuations in climate, ranging from intense greenhouse warming to icehouse cooling, which profoundly impacted the global depositional systems. The middle – upper Eocene deposits in Garet Gehannam, Fayum area, Egypt, present an exciting opportunity to explore paleoenvironmental dynamics using a multiproxy dataset of calcareous nannofossils, benthic foraminifera, ostracods, and molluscan assemblages. Calcareous nannofossil biostratigraphy constrained the studied sequence to the NP17 and NP-19-20 zones. Furthermore, three 3rd-order depositional sequences, BAR.SQ.1, BAR.SQ.2, and PR.SQ.3 were identified. The BAR.SQ.1 sequence encompasses the Gehannam Formation, with a transgressive systems tract (TST) and a highstand systems tract (HST). The BAR.SQ.2 sequence corresponds to the lower Birket Qarun Formation and exhibits a TST/HST pattern. The PR.SQ.3 sequence, however, consists solely of a TST spanning the upper Birket Qarun and Qasr El Sagha formations. The main trend of our multiproxy-based sea level curve shows an overall stepped Tethyan sea level regression within the 2nd-order cycle. This regression is characterized by a transition from outer neritic to inner settings, interrupted by two minor 3rd-order transgressive pulses. This sea level trend was likely driven by global eustatic changes and regional tectonic uplift related to the final collisional phase between Africa/Arabia and Eurasia, which led to the closure of the Neotethys Ocean. Multiproxy faunal analysis reveals a pronounced upsection shift from low-oxic and mesotrophic conditions to well-ventilated, oligotrophic settings tracking long-term sea level fall. The lowering of the sea level may have expanded aerobic ventilation windows on the continental shelf while potentially reducing nutrient influx. Our multiproxy sequence stratigraphic and paleoenvironmental analysis provides insights into the complex interplay of tectonic, eustatic, and climatic influences on the region during the middle – late Eocene episode along the southern Tethyan margin.

Shallow-water whale-fall communities: Evidence from the middle–late Eocene basilosaurid whale bones, Wadi El-Hitan, Fayum, Egypt

The present study examines the basilosaurid whale bone specimens collected from the Sandouk El-Borneta section, Wadi El-Hitan (Valley of Whales), Fayum, Egypt. These specimens are embedded in highly fossiliferous calcareous sandstones of the middle Eocene Gehannam and the upper Eocene Birket Qarun formations. These whale bones display some post-mortem alterations, representing good signs of at least three distinct stages in what is called the whale fall. The co-occurrence of shark, ray, and crocodile fossil specimens with the examined whale bones may indicate the first mobile-scavenger stage. Borings of the siboglinid polychaete genus Osedax represent the most common worm type that deeply bioeroded the whale bones, contributing to their rapid degradation, and representing the enrichment-opportunist stage. These fossil traces of the bone-eating worm Osedax represent the first record in the Eocene Epoch regionally and inter-regionally, filling the gap between the Late Cretaceous and the Oligocene occurrences. Subsequently, the studied whale bones served as hard substrates for some calcareous tube-dwelling encrusting polychaetes, balanoid barnacles, sheet‐like cheilostome bryozoans, and scleractinian corals. Furthermore, a bioerosion structure produced by polychaete annelids was also observed. The presence of these sclerobionts assemblage confirms the well-developed final reef stage with prolonged exposure and colonisation of these whale bones prior to final burial. Based on the recorded post-mortem alterations, together with other sedimentological and palaeontological data, the studied whale bones were deposited in a shallow open marine bay to sheltered gulf environments, which were characterised by low depositional energy, low to moderate rate of sedimentation, and high surface water productivity.

Mineralogy and geochemistry of elongated calcite-cemented concretions of the Upper Eocene Birket Qarun Formation (Fayum depression, Egypt): insights into concretions’ origin and paleoenvironmental implications

Mineralogy and geochemistry of elongated calcite-cemented concretions of the Upper Eocene Birket Qarun Formation (Fayum depression, Egypt): insights into concretions’ origin and paleoenvironmental implications

The Middle-Upper Eocene benthic foraminifera from north-west Fayoum area, Egypt: Paleoecology and their similarity to the Tethyan provinces

This study deals with the Middle–Late Eocene benthic foraminiferal assemblage from the Um Rigl succession that is exposed in the northwest of Fayoum area, Egypt. Stratigraphically, two rock units are recognized from base to top as the Gehannam Formation and Birket Qarun Formation. The examination of benthic foraminiferal community identifies 63 species belonging to 36 genera, 22 families and four suborders. Their distribution aids to recognize one benthic foraminiferal biozone, Bulimina jacksonensis-Uvegerina jacksonensis Zone. To detect the paleocological conditions that prevailed during the deposition of the studied succession, a quantitative analysis is done on the foraminiferal assemblage, including the number of taxa, the relative abundances of the recorded suborders, calcareous species, agglutinated species and common species. The morphology of benthic foraminiferal tests is strongly associated with their microhabitat preferences. Therefore, the percentages of epifaunal and infaunal species are also calculated to detect the level of oxygenation. Accordingly, two ecozones are established, ecozone 1 represents the Gehannam Formation, whereas ecozone 2 represents the Birket Qarun Formation (excluding the barren zone in the upper part). Ecozone 1 is dominated by calcareous species (90–100%) and infaunal species (38–99%), while epifaunal species range from 2 to 62%. The most abundant taxa are Bolivina, Bulimina, Uvigerina, Nonion and Lenticulina. Therefore, the ecozone 1 was deposited under an inner-outer neritic environment, with normal salinity and eutrophic to mesotrophic conditions. On the other side, ecozone 2 is characterized by changes in the composition of foraminiferal assemblage, where infaunal species dominate the base of this ecozone, followed by a strong decline in the middle part and then increase again in the upper part. Also, a notable increase in epifaunal species is documented in this ecozone. This variation in foraminiferal assemblage reflects changes in water depth and oxygen content. Consequently, ecozone 2 was deposited under an inner to middle neritic environment, with normal salinity and mesotrophic to oligotrophic conditions. Regarding the paleobiogeographic outline, the results of multivariate analyses indicate that the Egyptian species show a strong similarity to those from the Southern Tethyan Province (Tunisia and Libya), whereas they show a reasonable similarity to the Western Tethyan Province (Spain, Italy, France). This deduction reflects a probable marine connection between both provinces during Eocene.

Biostratigraphy, palaeoecology, and palaeobiogeography of the Middle–Late Eocene ostracods, north‐west Fayoum area, Egypt

The present study focuses principally on the late Middle Eocene–early Late Eocene ostracods from two successions (Garet Umm Rigl section and Qasr El Sagha sections), in the northwestern portion of Fayoum area, Egypt. Stratigraphically, the studied successions are classified into three formations (from base to top), the Gehannam, Birket Qarun, and Qasr El Sagha (Temple Member). The recorded ostracod assemblage contains 33 species belonging to 20 genera and 9 families. According to their stratigraphic ranges, three local biozones are recognized, Asymmetricythere yousefi–Loxoconcha pseudopunctatella, Reticulina heluanensis–Leguminocythereis sadeki, and Trachyleberis nodosus nodosulcatus–Ruggeria (Keijella) glabella. The comparison of the proposed biozones with their equivalents inside Egypt denotes a Middle–Late Eocene age for the studied sections. Based on the character of investigated ostracods, three ecozones are distinguished. An inner–outer neritic environment is suggested for the first ecozone, inner‐middle neritic conditions for the second, while shallow water conditions are proposed for the third ecozone. In addition, this paper represents an attempt to detect the palaeobiogeographic provinces of Eocene ostracods by means of multivariate analyses (principle component analysis, Q‐mode cluster analysis and similarity index). These analyses are applied on a matrix composed of some selected Eocene species from 10 regions located at the southern Tethys and western Africa. The results identify three distinctive provinces, North Africa (Algeria, Tunisia, Libya, and Egypt), the Middle East (Jordan and Israel) and West Africa (Senegal, Togo, Ivory Coast and Nigeria). The distinctive affinities between these provinces suggests ostracod migration along the southern Tethys during the Eocene age.

New records of legless squamates from the lowest upper Eocene deposits of the Fayum Depression, Egypt

ABSTRACT The Eocene was a key interval for the diversification of squamates worldwide. However, little is known about their early evolution in Africa due to the scarcity of Paleogene fossil squamates from that continent. One of the most important Eocene vertebrate assemblages in Africa is known from the Fayum Depression of Egypt, but only a few lizards and snakes have been reported from these deposits. Here we report the first Paleogene record of the clade Amphisbaenia in Egypt, from the lowest upper Eocene Birket Qarun Locality 2 (BQ-2). It corresponds to a mid-trunk vertebra characterized by a depressed centrum with a flattened base, hemispherical synapophyses, and absence of a neural spine. Additional material from BQ-2 includes seven vertebrae attributed to colubroidean snakes. One trunk vertebra resembles those of early Eocene Procerophis from India while the remaining colubroidean vertebrae are referred to Renenutet enmerwer. Caudal vertebrae of Renenutet are described here for the first time. Similarities in the caudal vertebral morphology between BQ-2 Renenutet and Thaumastophis missiaeni from the lower Eocene of India reinforce the hypothesis of a close affinity between them. The presence of cf. Procerophis and Renenutet in Egypt adds to the evidence for terrestrial faunal exchange between Asia and northern Africa during the early/middle Eocene along the southern margin of the Tethyan Sea.

Sequence stratigraphic framework of the Upper Eocene–Oligocene succession, northwest Birket Qarun, Fayum-Egypt

The Upper Eocene–Oligocene sequence exposed northwest Birket Qarun; Fayum district covers two rock units, Qasr El-Sagha (Temple and Dir Abu Lifa members) and Gebel Qatrani formations were re-evaluated by sequence stratigraphy. Six depositional sequences were recognized based on facies geometry, and sedimentological aspects. The first sequence (Temple Member) was accumulated under marginal intertidal flat environment indicating highstand deposits. The second (the lower Dir Abu Lifa Member) displays a regressive sedimentary facies starting with progradational delta front environment reflecting lowstand deposits followed upward by a lagoonal environment indicating transgressive/highstand deposits. The third (the top of the Dir Abu Lifa Member) was accumulated under a low sinuosity stream reflecting lowstand deposits. The fourth which constitutes the topmost of Dir Abu Lifa Member initiating near-shore shallow marine points to transgressive sediments, followed upward by fluvial sediments reflecting highstand deposits. The fifth (the Lower of Gebel Qatrani Formation) accumulated as point-bar deposits demonstrating lowstand deposits. The last occupies the main of Gebel Qatrani Formation initiates with restricted riverine marking lowstand deposits, followed upward by several fining upward cycles that were accumulated in fluvial and flood plain conditions with evidence of tidal influence on sedimentation near its top denoting transgressive deposits. Several minor transgressive episodes accompanied by tidal influence on sedimentation are noticed near the top, which may reflect gradual subsidence of the Oligocene alluvial plain. The area is subjected to relative sea-level changes that show a similarity with the global sea level. The base-level fluctuations are mainly controlled by the regional tectonic setting.

The earliest recorded fossil pelican, recovered from the late Eocene of Wadi Al-Hitan, Egypt

ABSTRACT The Paleogene record of pelicans (Pelecanidae) is represented at present by a single early Oligocene specimen from southeastern France. Here we describe a new pelecanid from the early Priabonian portion of the Birket Qarun Formation within the Wadi Al-Hitan World Heritage Site in Egypt. This specimen, a nearly complete right tibiotarsus, is the first definitive pelecanid recovered from Eocene strata. The tibiotarsus is remarkably similar to those of known Pelecanus species, but sufficiently different to warrant designation as the new genus and species Eopelecanus aegyptiacus. This represents the oldest pelican described to date and extends the pelecanid fossil record by ca. 6 million years.

A New Specimen of Xiphiorhynchus sp. cf. aegyptiacus (Istiophoriformes, Xiphioidei, Xiphiidae) and Billfish Diversity in the Oligocene of South Carolina

A partial billfish rostrum from the Chandler Bridge Formation (Early Chattian, Oligocene) near Ladson, South Carolina, U.S.A., is described and identified as Xiphiorhynchus sp. cf. aegyptiacus. The angle of taper, depth to width ratio of the cross section, and other morphological features (including dorsolateral grooves and a planoconvex cross-section), indicate that this specimen (and an earlier published speccimen) is closest in morphology to X. aegyptiacus from the Eocene Birket Qarun Formation of Egypt. This confirms the presence of a second xiphiid in the Chandler Bridge Formation besides the well-documented giant swordfish X. rotundus. This is an unusual example of two Xiphiorhynchus species existing in known sympatry, and strongly contrasting morphologies and morphometrics may point to niche partitioning between the two forms. The occurrence of specimens strongly resembling X. aegyptiacus in the western Atlantic also further substantiates past arguments that easy dispersal across the Atlantic was possible for this genus, and, by extension, that it shared the open-sea, migratory epipelagic lifestyle of modern swordfish. Moreover, the Chandler Bridge Formation boasts the most diverse billfish assemblage in the world, including Xiphiorhynchus sp., cf. X. aegyptiacus, X. rotundus, an early istiophorid, and 4-7 species of blochiid billfish in the genera Aglyptorhynchus and Cylindracanthus.

Oldest Record of African Bagridae and Evidence from Catfishes for a Marine Influence in the Late Eocene Birket Qarun Locality 2 (BQ-2), Fayum Depression, Egypt

ABSTRACT The Birket Qarun Formation, sampling upper Eocene deposits of the Fayum Depression, has been the subject of disagreement in terms of the environmental deposition. The formation has traditionally been considered to be a marine deposit but, more recently, one particular site, Birket Qarun Locality 2 (BQ-2), has been reported to have freshwater vertebrates, indicating that at least this locality in the formation contains terrestrial deposits. We here report a new varied assemblage of fossil catfishes from BQ-2, which adds new information with which to interpret the paleoenvironment of the locality. The new BQ-2 catfish assemblage includes the earliest record of the freshwater family Bagridae in Africa, as well as the oldest records of Fajumia and Socnopaea, otherwise known only from the overlying marine deposits of the Qasr el-Sagha Formation. Notable among the finds are remains of Arius fraasi and two additional species of marine ariid catfishes, representing the first such occurrences from the Fayum deposits. These occurrences indicate that BQ-2 likely had marine influences, or perhaps that Fajumia, Socnopaea, and Arius were euryhaline. In addition, the freshwater families Claroteidae and Mochokidae are represented among our collection. The new material documents the presence of a variety of taxa, and in addition it documents the variation in body size of members of the same family. Most evidence from other vertebrate fossils indicates that BQ-2 is a freshwater deposit, but some elements of the new catfish collection suggest the presence of nearshore marine influences, indicating that a much more complex environment was present.

New Crocodylomorph Material from the Fayum Depression, Egypt, Including the First Occurrence of a Sebecosuchian in African Late Eocene Deposits

ABSTRACT During the Cretaceous and Paleogene periods, the Earth experienced tectonic and climatic changes, which included continental drift following the breakup of the supercontinents Gondwana and Laurasia, the end-Cretaceous mass extinction event, and several climatic events, including the Paleocene–Eocene Thermal Maximum and the Middle Eocene Climatic Optimum. In response to increased temperatures and vacancies of ecospace left by the extinction of non-avian dinosaurs, mammal and reptile lineages that survived into the Eocene underwent immense evolutionary radiations that led to the diversification of crown clades, such as Crocodylia. Late Eocene deposits in northern Africa provide insights into how crocodyliforms responded to these tectonic and climatic events. Specifically, the Birket Qarun Formation in the Fayum Depression of Egypt contains several species of crown crocodylians as part of its rich fossil record of vertebrates. This study provides description of new material attributable to crocodylian taxa previously known from this formation, as well as newly recognized non-crocodylian mesoeucrocodylian material referable to Sebecosuchia. The sebecosuchian material provides important evidence attesting to the diversity of crocodyliforms in the late Eocene of Africa and expands the known biogeographic range of sebecosuchians.

Fossil burrow assemblage, not mangrove roots: reinterpretation of the main whale-bearing layer in the late Eocene of Wadi Al-Hitan, Egypt

The UNESCO World Heritage Site of Wadi Al-Hitan near Fayum in the Western Desert of Egypt is well-known for its remarkable abundance and diversity of late Eocene marine fossils, especially well-preserved cetaceans and sirenians. However, the taphonomy of the early Priabonian whales and sea cows is still not fully understood. These marine mammals often occur on specific horizons in the Birket Qarun Formation, for example, on a distinctive firmground called the Camp White Layer (CWL). Vertical, rod-like structures in the CWL were previously interpreted as “mangrove pneumatophores,” which have influenced hypotheses about the habitat of early whales. Here, we reexamine the rod-like structures of the CWL and show that they do not represent mangrove rooting structures based on an analysis of their morphology and an extensive comparison with rooting structures of living mangroves. Instead, the morphology of the rod-like structures indicates that they are trace fossils representing five size classes of marine invertebrate burrows, including burrows of weakly umbonate clams and Ophiomorphidae. The complex overprinting of all burrows toward the top of the CWL indicates stratigraphic condensation caused by low overall rates of sedimentation on a marine flooding surface in the transgressive systems tract. The large number of whale carcasses, abundant invertebrate skeletal remains, logs, marine invertebrate-encrusted celestine crystals, and an extensive, diverse burrow network reflect a combination of environmental and temporal condensation. A peculiar feature of the CWL, celestine crystal aggregates and gastropod celestine pseudomorphs, indicate an evaporative phase that is difficult to reconcile with the current sequence stratigraphic framework.

On the Eocene mangroves of Wadi Al-Hitan World Heritage site, Fayum, Egypt

Wadi Al-Hitan is the first site in Egypt to be inscribed by UNESCO on the “Natural World Heritage List”. Wadi Al-Hitan mangrove plant bed lies in late middle Eocene (Bartonian) at the top of Birket Qarun Formation, underlying Qasr El-Sagha Formation (Priabonian). Plant fossils include casts of roots and rhizomes, an impression of a leaf and petrified drift woods. Problematic fossils include directly–preserved hard parts of Echinodermata and casts of closely-spaced, mineral-filled siphons of bivalves. All fossils are described, illustrated and discussed in detail.

Taxonomy and morphological study on the vertebrate remains of Shark and rays fauna from the Middle and Late Eocene succession, Fayoum Depression, Egypt

Well preserved vertebrate remains of Shark and ray fauna from the Middle and Late Eocene succession ofFayoum depression, at Gebal Qasr El-Sagha area have been documented and studied in details. Four stratigraphic sectionsare measured, described and sampled in the field at Hussein Wally Village, Birket Qarun, Qasr el-Sagha and Wadi el-Afreet. Lithostratigraphically, the studied succession is divided into three formations arranged from base to top intoGehannam, Birket Qarun and Qasr el-Sagha formations. This Eocene sequence provides by far the most complete view ofthe endemic African vertebrate fauna. Identification of the basic pattern of fish remains and taxonomic evaluation revealedthat the recorded shark and rays taxa belong to 3 classes, 7 orders, 12 families, 18 genera, and 21 species. The identifiedtaxa are macro-scale, collected on the surface, and known either from teeth or rostral remains. A taxonomic account anddetailed morphologic description of the fossils shark, rays and bony fish teeth have been achieved. The depositionalenvironments in the studied Middle-Late Eocene age sequence are interpreted. The abundance of recognized vertebratefauna indicates environments varying from open marine shelf with low energy conditions to restricted marine shallowwater conditions. However, the frequent distribution of macrofauna with intense bioturbation in sandstones of Birket QarunFormation is a good indicator of restricted shallow water conditions.

A new genus and species of marine catfishes (Siluriformes; Ariidae) from the upper Eocene Birket Qarun Formation, Wadi El-Hitan, Egypt.

Wadi El-Hitan, the UNESCO World Heritage Site, of the Fayum Depression in the northeast part of the Western Desert of Egypt, has produced a remarkable collection of Eocene vertebrates, in particular the fossil whales from which it derives its name. Here we describe a new genus and species of marine catfishes (Siluriformes; Ariidae), Qarmoutus hitanensis, from the base of the upper Eocene Birket Qarun Formation, based on a partial neurocranium including the complete left side, partial right dentary, left suspensorium, two opercles, left pectoral girdle and spine, nuchal plates, first and second dorsal spines, Weberian apparatus and a disassociated series of abdominal vertebrae. All of the elements belong to the same individual and some of them were found articulated. Qarmoutus gen. nov. is the oldest and the most complete of the Paleogene marine catfishes unearthed from the Birket Qarun Formation. The new genus exhibits distinctive features not seen in other African Paleogene taxa, such as different sculpturing on the opercle and pectoral girdle with respect to that on the neurocranium and nuchal plates, denticulate ornamentation on the skull bones arranged in longitudinal rows and forming a radiating pattern on the sphenotic, pterotic, extrascapular and the parieto-supraoccipital, indentations or pitted ornamentation on the nuchal plates as well as the parieto-supraoccipital process, strut-like radiating pattern of ornamentation on the opercle from the proximal articulation to margins, longitudinal, curved, reticulate ridges and tubercular ornamentations on the cleithrum, sinuous articulation between the parieto-supraoccipital process and the anterior nuchal plate, long, narrow, and arrowhead shaped nuchal shield, very small otic capsules restricted to the prootic. Multiple parsimony and Bayesian morphological phylogenetic analyses of Ariidae, run with and without “molecular scaffolds”, yield contradictory results for the placement of Qarmoutus; the genus is either a phylogenetically basal ariid, or it is deeply nested within the ariid clade containing New World species of Sciades.

A New Family of Large Omnivorous Bats (Mammalia, Chiroptera) from the Late Eocene of the Fayum Depression, Egypt, with Comments on Use of the Name “Eochiroptera”

ABSTRACT A new fossil from the Late Eocene BQ-2 locality in the Birket Qarun Formation in the Fayum Depression of northern Egypt (dated to ~37 mybp) does not fit within the diagnosis of any previously described family of bats from Africa or any other continent. Known from a partial maxilla, this taxon has dilambdodont tribosphenic molars with a well-developed, symmetrical, W-shaped ectoloph lacking a distinct mesostyle but with a strong parastyle and shallow U-shaped ectoflexus—all traits that are found in most archaic bat families and that are probably plesiomorphic for bats. However, this taxon also has an M2 with a large metaconule cusp and a large, bulbous hypocone set low on the posterolingual corner of the tooth, neither of which occur in any known bat family, living or extinct. Also notable is the size of the new BQ-2 bat, which appears to have been approximately the same size as the largest extant bats with dilambdodont dentitions, falling well within the size range of plant-eating megabats and ca...

Facies transition and depositional architecture of the Late Eocene tide-dominated delta in northern coast of Birket Qarun, Fayum, Egypt

Late Eocene successions in the Fayum Depression display notable facies transition from open-marine to brackish-marine realms. Stratigraphic and sedimentologic characteristics of the depositional facies are integrated with ichnological data for the recognition of four facies associations (FA1 to FA4). The transition from open-marine sandstones (FA1) to the brackish-marine deposits (FA2) heralds a transgressive – regressive dislocation. The shallowing- and coarsening-upward progradation from the basal prodelta mudstone-dominated facies (FA2a) to deltafront heterolithics (FA2b) and sandstone facies (FA2c) are overlain by finning-upward delta plain deposits which are expressed by the delta plain mudstone (FA2d) and erosive-based distributary channel fills (FA4). Prodelta/deltfront deposits of FA2 are arranged in thinning- and coarsening-upward parasequences which are stacked in a shallowing-upward progressive cycle. Shallow-marine fossiliferous sandstones (FA3) mark the basal part of each parasequence. Stratigraphic and depositional architectures reflect a tide-dominated delta rather than an estuarine and incised valley (IV) model. This can be evinced by the progressive facies architecture, absence of basal regional incision or a subaerial unconformity and the stratigraphic position above a maximum flooding surface (MFS), in addition to the presence of multiple tidally-influenced distributary channels. Stratigraphic and depositional characteristics of the suggested model resemble those of modern tide-dominated deltaic systems. Accordingly, this model contributes to our understanding of the depositional models for analogous brackish-marine environments, particularly tide-dominated deltas in the rock record.

Egyptian diatomite as high fluid loss squeeze slurry in sealing fractures and high permeable formation

Lost circulation is the most costly mud related drilling problem, and induced fracture. Water slurry of diatomite is used as the high fluid loss squeeze slurry in the treatment of lost circulation and in decreasing fluid loss. Egypt has diatomite deposits, especially in El-Fayuom Depression. Fourteen samples were collected from Qasr El-Sagha at the northern shore of Birket Qarun. Samples were examined to identify the diatom species then subjected to X-ray fluorescence, XRD and grain size distribution tests. A total of 38 species related to 13 diatom genera were identified. Cocconeis, Epithemia and Rhopalodia were the predominant genera. The diatomaceous earth which acts as a filter aid material was tested with different additives; bentonite, lime, finely divided paper, polymer, barite and different concentrations with different types of lost circulation materials (LCM) to form a high fluid loss squeeze slurry. As a result the required time for collecting the filtrate was decreased to be in the range of 50s to 1min and 49s comparing with the international standard which recommended the filtrate should be collected maximum within 2–3min.

A Fish Assemblage from the Middle Eocene from Libya (Dur At-Talah) and the Earliest Record of Modern African Fish Genera.

In the early nineteen sixties, Arambourg and Magnier found some freshwater fish (i.e., Polypterus sp., Siluriformes indet. and Lates sp.) mixed with marine members in an Eocene vertebrate assemblage at Gebel Coquin, in the southern Libyan Desert. This locality, aged ca 37–39Ma and now known under the name of Dur At-Talah, has been recently excavated. A new fish assemblage, mostly composed of teeth, was collected by the Mission Paléontologique Franco-Libyenne. In this paper, we describe freshwater fish members including a dipnoan (Protopterus sp.), and several actinopterygians: bichir (Polypterus sp.), aba fish (Gymnarchus sp.), several catfishes (Chrysichthys sp. and a mochokid indet.), several characiforms (including the tiger fish Hydrocynus sp., and one or two alestin-like fish), and perciforms (including the snake-head fish Parachanna sp. and at least one cichlid). Together with the fossiliferous outcrops at Birket Qarun in Egypt, the Libyan site at Dur At-Talah reduces a 10-Ma chronological gap in the fossil record of African freshwater fish. Their fish assemblages overlap in their composition and thus constitute a rather homogenous, original and significant amount of new elements regarding the Paleogene African ichthyofauna. This supports the establishment of the modern African freshwater fish fauna during this time period because these sites mostly contain the earliest members known in modern genera.

Bone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the late Eocene of Egypt estimated by finite element analysis.

Bite marks suggest that the late Eocence archaeocete whale Basilosaurus isis (Birket Qarun Formation, Egypt) fed upon juveniles of the contemporary basilosaurid Dorudon atrox. Finite element analysis (FEA) of a nearly complete adult cranium of B. isis enables estimates of its bite force and tests the animal’s capabilities for crushing bone. Two loadcases reflect different biting scenarios: 1) an intitial closing phase, with all adductors active and a full condylar reaction force; and 2) a shearing phase, with the posterior temporalis active and minimized condylar force. The latter is considered probable when the jaws were nearly closed because the preserved jaws do not articulate as the molariform teeth come into occulusion. Reaction forces with all muscles active indicate that B. isis maintained relatively greater bite force anteriorly than seen in large crocodilians, and exerted a maximum bite force of at least 16,400 N at its upper P3. Under the shearing scenario with minimized condylar forces, tooth reaction forces could exceed 20,000 N despite lower magnitudes of muscle force. These bite forces at the teeth are consistent with bone indentations on Dorudon crania, reatract-and-shear hypotheses of Basilosaurus bite function, and seizure of prey by anterior teeth as proposed for other archaeocetes. The whale’s bite forces match those estimated for pliosaurus when skull lengths are equalized, suggesting similar tradeoffs of bite function and hydrodynamics. Reaction forces in B. isis were lower than maxima estimated for large crocodylians and carnivorous dinosaurs. However, comparison of force estimates from FEA and regression data indicate that B. isis exerted the largest bite forces yet estimated for any mammal, and greater force than expected from its skull width. Cephalic feeding biomechanics of Basilosaurus isis are thus consistent with habitual predation.