Chapter 9

The Eocene Mammalian Fauna of Chambi (Tunisia) in Its Geological Context

JEAN-LOUIS HARTENBERGER, JEAN-YVES CROCHET, CLAUDE MARTINEZ, BERNARD MARANDAT, and BERNARD SIGE

1. Introduction . . . . . . . . . . . . . . · .237 2. Paleogeography and Biostratigraphy · .238 3. Continental Paleogene Series .... · .238 4. Summary of Chambi Vertebrates .. ......... 244

References . . . . . . . . . . . . . . . . ........ 249

1. Introduction

In the Kasserine area of Tunisia there is a Cenozoic basin containing Paleogene continental deposits. Palustrine limestones located at the base of the Paleogene series have yielded the Chambi mammalian fauna. Representatives of the

JEAN-LOUIS HARTENBERGER • Laboratoire de Paleontologie, Institut des Sciences de l'Evo­lution, CC64, Universite Montpellier II, 34095 Montpellier Cedex 5, France. JEAN-YVES CROCHET • Laboratoire de Paleontologie, Institut des Sciences de l'Evolution, CC64, Univer­site Montpellier II, 34095 Montpellier Cedex 5, France. CLAUDE MARTINEZ • ORSTOM Geofluides, Bassins, Eaux, CC58, Universite Montpellier II, 34095 Montpellier Cedex 5, France. BERNARD MARANDAT • Laboratoire de Paleontologie, Institut des Sciences de l'Evolution, CC64, Universite Montpellier II, 34095 Montpellier Cedex 5, France. BERNARD SIGE • Centre de Paleontologie stratigraphique et Paleoecologie, Universite Lyon I, 69622, Villeurbanne, France.

Eocene Biodiversity: Unusual Occurrences and Rarely Sampled Habitats, edited by Gregg F. Gunnell, Kluwer Academic/Plenum Publishers, New York, 2001.

237

238 Chapter 9

following mammalian orders and families have been found: Marsupialia, Peradectidae; Placentalia, Protheutheria indet.; ?Lipotyphla, ?Erinaceomorpha; Chiroptera, Rhinolophoidea, Nycterididae and Vespertilionoidea, Philisidae; Primates, Adapidae; Rodentia, Zegdoumyidae; Macroscelidea, Herodoti­nae; Hyracoidea, Pliohyracidae. The analysis of this local fauna provides insights into its position with regards to other North African mammalian faunas and its possible relationships with Eocene Eurasian faunas.

2. Paleogeography and Biostratigraphy

The first paleogeographic maps of Thnisia were published By Flandrin (1948). This author described the "Kasserine Island," an area he considered as an emer­gent land mass during the Eocene in the eastern Tethys Seaway. This paleo­geographic concept was clarified by Burollet (1956) in his review of the stratigraphy of Tunisia. He believed that the "Kasserine Island" was present from the Senonian (= late Cretaceous, Coniacian through Maastrichtian) to the Miocene. As shown in Figure 1, the area of the "Kasserine Island" is situated in central Thnisia, north of the Jeffara Mole. One of the highest mountains of this region is the Chambi Massif that reaches an elevation of 1544 meters. The structure of this massif is made up of folded and faulted Cretaceous marine limestones attributed to the Abiod Formation (Burollet, 1956). Paleogene red continental sediments lie unconformably on the folded Cretaceous limestones and are mostly situated north of the Chambi Massif summit. Above the conti­nental Paleogene sequence (which is 100 to 150 meters thick) there are uncon­formable Miocene deposits. These Miocene rocks have been tentatively correlated with the Beglia Formation (Biely et aJ., 1972). A general geological setting of the Chambi Massif is shown in Figure 2.

Lacustrine and terrestrial gastropods (mostly internal molds) previously were the only fossils available for dating the Paleogene formation at Chambi (Sassi et al., 1984). Subsequent studies of charophytes in North Africa (Mebrouk, 1993; Mebrouk et aJ., 1997) have shown that the base of the Paleogene formation is early Eocene in age and the top of the sequence is late Eocene or early Oligocene in age. The first fossil mammals were found in 1985 (Hartenberger et al., 1985).

3. Continental Paleogene Series

As illustrated in Figures 3 through 5, the Paleogene sediments, which are about 100 to 150 meters thick, represent a complex geological history in this area. At the base, fluvial conglomerates predominate with polygenic elements of decimeter size enclosed in a calcitic, sandy cement. These conglomerates are distributed in meter thick lenses and are overlain by thin beds (10 cm) of lacus­trine or palustrine limestones. The mammal bones and teeth are found some 30m above the base of the Paleogene series in a massive lacustrine limestone

The Eocene Mammalian Fauna of Chambi (Tunisia) 239

FIGURE 1. Palaeogeographic map of Tunisia during the Eocene with the Chambi mammalian locality indicated (modified from Sassi et aJ., 1984).

layer with beds ranging from 30 cm to 1 m in thickness. The charophytes men­tioned above occur in a marl horizon at the bottom of the limestones. At the top ofthe fossiliferous limestones, conglomerates again occur, but with smaller clasts than at the base. The upper part of the Paleogene series is made up of sands with rubefied traces indicating an interruption deposition and the onset of weathering. Above these sands thick lacustrine or palustrine limestones con­taining gypsum crystals are found. These limestones are generally distributed in thinner beds than the sequence containing the vertebrate fossils. Gastropod molds are frequently found in this upper limestone unit and have been iden­tified as Bu1iminus and Pa1aeocyclotus (Sassi et a1., 1984). Charophytes also are relatively common in these limestones. The Paleogene series ends with sandy clays containing fossil plants and charophytes. Miocene deposits uncon­formably overlie the Paleogene sequence.

Continental formations similar to those at Chambi have been described from the Paleogene of southern France and in some cases these "lacustrine lime­stones" have yielded isolated vertebrate fossils. At a few French localities a

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Chapter 9

FIGURE 4. Composite geological section showing lithological succession as observed in the north­ern Chambi area and position of gastropod and vertebrate localities.

diverse mammalian fauna has been recovered from deposits similar to Chambi, especially in Aumelas, near Montpellier (Hartenberger, 1963). These limestones are distributed in various small basins as illustrated in 1/50,000 geological maps of the Montpellier and Saint Martin de Londres areas. In fact all of these lacus­trine basins can be considered as part of a larger system, the "Lutetian lake," that covered most ofthe Languedoc area during the Middle Eocene. A synthetic overview of continental Paleogene formations of Southern France is given in

The Eocene Mammalian Fauna of Chambi (Tunisia) 243

Cavelier (1984) in which most mammalian localities have been taken into con­sideration. Considering the only "lacustrine" limestones, Freytet (1973) noted that the carbonate facies of these formations can be of several types including: limestones deposited in fluvial channels; true lacustrine limestones with sub­aqueous diagenetic evolution; or palustrine limestones resulting from emersion of lacustrine muds frequently affected by soil processes.

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244 Chapter 9

200 X 50 meter area and up to now it has been impossible to locate concen­trations of bone. Fossils are obtained by dissolving limestone blocks in dilute solutions of acetic or formic acid following a method summarized by Orth (1987). At present, 500kg of limestones have been dissolved. Blocks are selected in the field when small bones occur on the surface or after breaking the limestones open and finding evidence of bone. Finds of teeth in the field are rare but the presence of small bones is relatively frequent. Nevertheless, it appears now that the occurrence of "good" fossils in these limestones is very irregular and many blocks lack any bone at all. As the fossils are very fragile, the acid preparation process takes a great deal of time and requires frequent water washing of the blocks and many applications of glue to the fossils. It takes approximately one month to dissolve a 3 kg block with an 8% acid solu­tion. Only a few relatively complete dentitions have been found (Figure 7) and isolated teeth are frequently broken or worn. Table 1 presents a list of the biotic elements so far discovered from Chambi.

4. Summary of Chambi Vertebrates

An extensive and critical review of the mammals and other fossils found in the Chambi area and their taxonomic status can be found in Hartenberger et al. (1997). The main conclusions of these authors concerning the biostrati­graphic position of Chambi in comparison to other Paleogene North African and Arabian localities are summarized here (Figure 6). The age of the Pale­ocene and early Eocene localities of Morocco is based on their selachian faunas (see Gheerbrant et al., 1993), but the precise locality where the Paleocene pro­boscidean Phosphatherium (Gheerbrant et al., 1998) was found is unknown. The Algerian and Tunisian localities have been correlated by charophyte studies (Mebrouk et aJ., 1998). These authors noted that many taxa found at these localities also are known in the Paleogene formations of Europe where a biochronological distribution of charophytes has been known for a long time (Rivelines, 1986). The positions of Fayum and Oman localities in Figure 6 follow the conclusions drawn respectively by Gingerich (1993) and Pickford et aJ. (1994). The position of Zallah in Libya follows the work of Fejfar (1987).

In fact, the stratigraphic position of all of these localities is in a state of flux and there is no doubt that in the future their relative stratigraphic posi­tions will be revised. One of the problems is that very few taxa have large geo­graphic distributions. This is compounded by the fact that specimens in hand are often fragmentary or poorly preserved. As an example, only two species found at Chambi have been recognized from other North African Paleogene localities: the charophyte Raskyella sahariana has been found at Gour Lazib and Glib Zegdou in Algeria (Mebrouk et aJ., 1997); and the rodent Zegdoumys sbetlai is present at Glib Zegdou. At the genus level, the Chambi hyracoid Titanohyrax also is present at Glib Zegdou (T. mongereaui) and in the Fayum (3 species). The Chambi adapid primate Djebelemur also is present in Algeria (contra Godinot, 1994). At the family level, affinities have been recognized

The Eocene Mammalian Fauna of Chambi (Tunisia) 245

between Chambi forms and some early Eocene European families of marsupi­als, primates, chiropterans, and condylarths. It appears that near the Paleocene­Eocene transition, interchanges between Africa and southern European mammalian terrestrial faunas were possible, but the direction of these exchanges cannot be determined at this time. North African, as well as Euro­pean, mammalian faunas were isolated during most of the Eocene. It is well

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246 Chapter 9

A

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The Eocene Mammalian Fauna of Chambi (Tunisia) 247

Table 1. List of biota collected from Chambi limestone, Chambi Massif, Tuisia Charophytes:

Raskyella cf. R. sahariana Mebrouk, 1993 Vertebrata:

Amphibia Batraciens indet.

Reptilia Squamata indet.

Mammalia Metatheria

Marsupialia Peradectidae

Kasserinotherium tunisiellse Crochet, 1986 Eutheria

?Lipotyphla ?Erinaceomorpha

GhambiJentes foussanensis (Gheerbrant and Hartenberger, 1999) Chiroptera

Rhinolophoidea Nycterididae

gen. et sp. indet. Vespertilionoidea

Philisidae Dizzya exsultalls (Sige, 1991)

Primates Adapidae

Djebelemur martillezi Hartenberger and Marandat, 1992 Rodentia

Zegdoumyidae Zegdoumys sbetlai Vianey-Liaud et al., 1994

Macroscelidea Chambius kasserillellsis Hartenberger, 1986

Hyracoidea Pliohyracidae

Titanohyrax talltulus Court and Hartenberger, 1993 Order indet.: in Court, 1993

FIGURE 7. Best preserved specimens of mammals found at Chambi (1984 expedition). All spec­imens are in the collections of the Service de la Carte Geologique, Office National des Mines, Tunis. A. Hyracoidea-Titanohyrax tantulus Court and Hartenberger, 1992, right maxilla with dP4-M2, holotype. Scale bar = 10 cm. Band C. Macroscelidea-Chambius kasserinensis Hartenberger, 1986, right maxilla with P4-M3, holotype (B) and left dentary with ml-3 (C). Scale bar = 1 mm. D-F. Primates-Djebelemur martinezi Hartenberger and Marandat, 1992, left dentary with p3-m3, holotype in occlusal (D), lateral (E), and medial (F) views. Scale bar = 1 mm. Figure A is repro­duced by permission of the Palaeontological Association. Figures B and C are from Hartenberger, 1986 and are reproduced by permission of the Institut de France. Academie des Sciences. Service des Comptes rendus. Figures D-F are reproduced by permission of the Instituto di Antropologia. Universite di Firenze.

248 Chapter 9

known that the end of the Eocene, marked by the Grande Coupure event, ter­minated this endemic period in Europe. A similar event probably occurred in North Africa but the appearance of anthracotheriids of Asian origin in the Oligocene of Fayum is, for the moment, the only supporting evidence.

The main interest of the Tunisian Chambi locality lies in the fact that the oldest occurrences on the African continent of representatives of Marsupialia and the eutherian orders Chiroptera, Macroscelidea, Hyracoidea, and Roden­tia have been found there.

Crochet (1986) notes that the marsupials found at Chambi show affinities with European genera. He points out that Asian, European, and African mar­supials otherwise known from the Eocene through Miocene, have restricted biogeographical ranges with only peradectines known from areas south of Tethys and herpetotheriids only known from areas north of Tethys. The fact that peradectine marsupials are present at Chambi suggests that some faunal interchange between the "Kasserine Island" and continental Europe may have been possible during the Eocene.

Among bats, the taxa represented at Chambi are members of the modern families Rhinolophoidea and Vespertilionidea. At the same time in Europe, only archaic groups of bats (archeonycterids, paleochiropterygids, hassianyc­terids) have been found. Based on this pattern of distribution, the African Paratethyean may be interpreted to have played an important role as a center of origin and subsequent dispersion of the modern bat clades. Recent discov­eries in Europe may qualify this point of view (Sige, 1997), but nevertheless, considering the age of Chambi with respect to that of European bat localities, it seems probable that transtethysan connections (from south to north), were still in existence at the end of the early Eocene (particularly for the paleochi­ropterygids).

The macroscelidid Chambius may share affinities with some condy­larthrans (Louisininae) from the Paris Basin. Recently Sudre et aJ. (1993) have noted the occurrence of louisinine condylarths from the Paleocene of Morocco, confirming the notion of faunal interchange between North Africa and Europe at the time of the Paleocene/Eocene transition. Also the primate Djebelemur looks very similar to European adapids that have been recovered from early Eocene deposits in southern France and the Paris Basin (Hartenberger and Marandat, 1992).

All of the rodents from Chambi are included in the family Zegdoumyidae. Some of the representatives of this family (Glibia, Glibemys) are probable ancestors of Anomaluridae, a family that is frequently considered to be the sister group of European Theridomyidae. Also it should be noted that some of the molars attributed to Zegdoumys from Chambi have a phiomyid tooth pattern, emphasizing the "African style" of the rodent fauna.

Titanohyrax tantulus from Chambi is presently the oldest known hyracoid. Court and Hartenberger (1993) examined the occlusal relationships of T. tantulus molars and concluded that their pattern of attrition is of a hyracoid type, not at all like the condition observed in earliest perissodactyls. This

The Eocene Mammalian Fauna of Chambi (Tunisia) 249

contradicts evidence pointing to a phylogenetic link between hyraxes and peris­

sodactyls as proposed by some authors (Fisher, 1986; Prothero et al., 1988). Overall the late-early to early-middle Eocene mammalian fauna from

Chambi has a relatively strong African character. At this time North Africa was

probably isolated from other areas as an island in the Tethys Seaway, but near

the Paleocene/Eocene transition exchanges were possible, particularly with

Europe.

ACKNOWLEDGMENTS. We are indebted to Dr. Ghozi and Dr. Ali Ben Hajl, Chiefs

of Service de la Carte Geologique (Office National des Mines, Tunis) and to Pro­

fessors Tlig and Zargouni (University of Tunis). Many thanks to M. Mansour and

Taleb Mohamed Tahar for facilities during field expeditions. Dr. G. F. Gunnell

read and improved an earlier version of the paper. All type specimens are in the

collections ofthe Office National des Mines (Tunis). N° I.S.E.M. 2001-016.

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