Zoological Journal of the Linnean Society

, 2006,

146

, 227–237. With 10 figures

© 2006 The Linnean Society of London,

Zoological Journal of the Linnean Society,

2006,

146

, 227–237

227

Blackwell Science, Ltd

Oxford, UK

ZOJZoological Journal of the Linnean Society

0024-4082The Lin-

nean Society of London, 2006? 2006

146

?

227237Original Article

A NEW POLYPTERID FROM THE LATE MIOCENE OF CHADO. OTERO ET AL.

*Corresponding author. E-mail: olga.otero@univ-poitiers.fr

A new polypterid fish:

Polypterus faraou

sp. nov. (Cladistia, Polypteridae) from the Late Miocene, Toros-Menalla, Chad

OLGA OTERO

1

*, ANDOSSA LIKIUS

2

, PATRICK VIGNAUD

1

and MICHEL BRUNET

1

1

Laboratoire de Géobiologie, Biochronologie et Paléontologie humaine, CNRS UMR 6046, Faculté des Sciences fondamentales et appliquées, Université Poitiers, 40 av. du Recteur Pineau, F-86 022 Poitiers cedex, France

2

Département de Paléontologie, Université de N’Djaména, N’Djaména, Tchad

Received June 2004; accepted for publication July 2005

Polypterus faraou

sp. nov.

(Cladistia, Polypteridae) from the Late Miocene of Toros-Menalla (western Djourab,Chad) is described on the basis of a subcomplete articulated skeleton preserved in three dimensions. This is the firsttime such a complete fossil polypterid skeleton has been described. It is the only verifiable fossil record for the genus

Polypterus

.

P. faraou

closely resembles

P. bichir

and

P. endlicheri

, extant fish found in the Chad–Chari system.Intrarelationships among the polypterids are not yet resolved: however,

P. faraou

shows a primitive shape of thebody and a primitive shape of the opening of the lateral line on the scales, similar to that of three living species(

P. bichir

,

P. endlicheri

and

P. ansorgii

). © 2006 The Linnean Society of London,

Zoological Journal of the LinneanSociety

, 2006,

146

, 227–237.

ADDITIONAL KEYWORDS: anatomy – Anthracotheriid Unit – Polypteriformes – western Djourab.

INTRODUCTION

Palaeontological expeditions have been conducted inChad since the early 1930s. In 1994, the MPFT(Mission Paléoanthropologique Franco-Tchadienne)initiated a series of field missions to the Mio-Pliocenesites of the eastern Djurab Desert in northern Chad(Brunet

et al

., 1995, 1998; Brunet & MPFT, 2000) and,since 1997, to the Miocene sites of Toros-Menalla,western Djurab. The Anthracoteriid Unit in Toros-Menalla has yielded a rich vertebrate fauna (Vignaud

et al

., 2002), the oldest known species of hominid,

Sahelanthropus tchadensis

(Brunet

et al

., 2002), aswell as the first nearly complete and articulated skel-eton of a fossil polypterid. This polypterid belongs to anew species that is described here. The estimated ageof the Anthracotheriid Unit is

c

. 7 Myr (Vignaud

et al

.,2002).

Polypterids (Cladistia) are basal actinopterygianfishes (Rosen

et al

., 1981). They are represented by

two extant genera, i.e.

Polypterus

, with ten species and15 subspecies (Poll, 1941a, b, 1942; Hanssens, Teugels& Thys van der Audenaerde, 1995; Britz, 2004; thereare 11 species if

P. polli

is considered as a valid spe-cies), and the monotypic genus

Erpetoichthys

. Ninefossil genera have been described. Two have beendescribed on the basis of isolated skull bones andscales (Meunier & Gayet, 1996; Gayet & Meunier,1991), and six others have been described on the basisof the articular head of pinnules (Gayet & Meunier,1996; Werner & Gayet, 1997). Finally,

Serenoichthys

has been described on the basis of scale and finletcounts and distribution (Dutheil, 1999).

Serenoichthys

is the only other fossil articulated skeleton known sofar, but the head is missing. These fossil genera areCretaceous in age and African, except for

Dagetella

and

Latinopollia

, which are of Late Cretaceous andEarly Palaeocene age, respectively, and South Ameri-can. Post-Palaeocene polypterid history is exclusivelyAfrican. Isolated scales and skull bones attributed to

Polypterus

sp. testify to the presence of the genus inAfrican freshwaters since the Eocene. Moreover, two

228

O. OTERO

ET AL.

© 2006 The Linnean Society of London,

Zoological Journal of the Linnean Society,

2006,

146

, 227–237

types of African Cretaceous pinnules were tentativelyattributed to two fossil

Polypterus

species,

P. dageti

(Gayet & Meunier, 1996) and

P. sudanensis

(Werner &Gayet, 1997). The intrarelationships among poly-pterids have yet to be clarified; indeed, the monophylyand the intrarelationships among extant species havenot been established.

This paper provides the first description of a nearcomplete fossil polypterid skeleton including cranium,and it is the only clearly recognizable fossil record forthe genus

Polypterus

. The new species from the LateMiocene of Toros-Menalla (western Djurab, Chad) isassigned to the genus

Polypterus

based on its morpho-logical characteristics, which fall within the anatomi-cal range of Recent species of the genus, from which itdiffers by a unique combination of characters. We alsodiscuss the primitive or derived state of certain osteo-logical features observed in this species.

SYSTEMATIC PALAEONTOLOGY

A

CTINOPTERYGII

C

OPE

, 1887(

SENSU

R

OSEN

ET

AL

., 1981)

CLADISTIA

COPE

, 1871P

OLYPTERIDAE

G

ÜNTHER

, 1870

P

OLYPTERUS

S

T

H

ILAIRE

, 1802

Type species. Polypterus bichir

St Hilaire, 1802.

P

OLYPTERUS

FARAOU

SP

.

NOV

.

Derivation of name

. In Chadian Arabian,

faraou

means flattened. The name is given in reference to thedorso-ventrally depressed head of the fish.

Type specimen

. TM090-001-039, housed in the CentreNational d’Appui à la Recherche (CNAR, N’Djamena,Chad).

Diagnosis

. A

Polypterus

species characterized by:depressed head (as in

P. weeksii

and

P. endlicheri

only), head length approximately 20% of body length(less than 20% in other

Polypterus

species except

P. ansorgii

,

P. bichir

and

P. endlicheri

) and head widthat the level of the preoperculum reaches 70% of itslength (more than in any other

Polypterus

species);opening of the lateral line on the nasal 3 close to itsposterior border (as in

P. bichir

and

P. endlicheri

,whereas it is central in other species); large androunded snout, shorter than the interorbital distance(as in most

Polypterus

species except

P. bichir

and

P. palmas

the snout of which is longer than theinterorbital distance); superolateral position of theorbit (as in

P. ansorgii

,

P. weeksii

,

P. endlicheri

and

P. bichir

, whereas the orbit is lateral in

P. delhezi

,

P. ornatipinnis

,

P. senegalus

,

P. retropinnis

and

P. palmas

); orbit length around the half the interor-

bital space (as in

P. bichir katangae

and possibly in

P. teugelsi

, whereas it is more than 60% in

P. ansorgii

,and less than 45% in the other species) and orbitsmaller than suboperculum width (as in

P. bichir

and

P. endlicheri

only); prognathus lower jaw (as in

P. bichir

and

P. endlicheri

only); at least 5–7 prespi-racular bones (the number of prespiracular bones ispossibly equal to or above seven only in

P. weeksii

, in

P. bichir bichir

and in

P. endlicheri congicus

); deepbody with approximately 23 transversal scales, 58–60scale rows, and 14 predorsal scales (such body shapeexists elsewhere only in

P. ansorgii

,

P. bichir

and

P. endlicheri

); 15 finlets with successive pinnules ofthe finlets overlapping the base of the followingone (such dorsal fin mophology elsewhere only in

P. ansorgii

,

P. bichir

and

P. endlicheri congicus

);grooved lateral line scales with notched posterior mar-gins (as in

P. ansorgii

,

P. bichir

and

P. endlicheri

only).The holotype is 590 mm in standard length. Such

dimensions are also reached in

P. bichir

and

P. endlicheri

only.

Occurrence. Anthracotheriid Unit of Toros-Menalla,Late Miocene of Chad.

MATERIAL AND METHODS

Specimen TM090-001-039 was found lying on its back.It is preserved in three dimensions. The dorsal andlateral body surfaces have globally kept their livingshape, whereas the ventral surface has collapsed(Fig. 1A–C). Most of the scales of the body are presentand articulated with each other. All the bones of theright half of the skull are in natural position, whereassome bones of the left side are slightly displaced. Thisthree-dimension preservation allows us to observe thenatural position of the bones and the shape of the cra-nium; it also allows us to measure the dimensions ofthe specimen (Fig. 2) and to compare some dimensionsand meristic data between the specimen and Recentspecies. Jollie’s (1984) nomenclature of the bones isfollowed.

ANATOMICAL DESCRIPTION

HEAD AND BODY SHAPE (FIGS 1–3)

The standard length of the specimen is 59 cm (Fig. 2,a). We observe a natural dorso-ventral depression ofthe head. The head length (from the front of the mouthto the posterior level of the opercular bone) is equiva-lent to about 20% of the standard length (Fig. 2, m).The width of the head, measured at the level of thepreoperculum, is around 70% of its length (Fig. 2, n).The distance between the lateral border of the spira-cular series at the level of the preoperculum is 45% ofthe total length of the head (Fig. 2, o). The lower jaw is

A NEW POLYPTERID FROM THE LATE MIOCENE OF CHAD 229

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prognathus. The general shape of the snout is wideand rounded, and it is shorter than the interorbitalspace is wide (Fig. 2, compare c and e). The orbit has asuperolateral position. The orbital length is 14% of thehead length (Fig. 2, p) and half the interorbital dis-tance (Fig. 2, q). The interorbital distance is shorterthan the orbit–spiracle distance. Posteriormost nasals

(nasals 3) meet in the midline. The suboperculum isdeeper than the orbit length. The gular plates aremore than twice as long as wide. The dorsal finletsinsert on the posterior five-sixths of the body. Theaxial skeleton is seen where the ventral scales are dis-placed. The left pelvic fin is preserved, whereas onlythe scaly base of the pectoral and anal fins and the

Figure 1. Photograph of specimen TM90-01-39, holotype of Polypterus faraou sp. nov., in A, dorsal, B, left lateral, andC, ventral views.

Figure 2. Measurements in specimen TM90-01-39, holotype of Polypterus faraou sp. nov., and ratios used in the text.

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proximal part of some caudal rays are preserved. Theposition of the fins is given (Fig. 2, h–l).

SNOUT, ORBIT AND UPPER JAW (FIG. 4)

The INTERNASAL (median rostral) is the unpaired dia-mond-shaped bone at the front of the head. It carriesthe ethmoid commissure. It lies dorsal to the rostro-premaxillae, and inserts laterally between the nasals2, and posteriorly between the nasals 3.

The paired nasal bones and the nostrils are in placeon the left side but slightly displaced on the right.NASAL 1 is a curved tubular bone, where the infraor-bital canal runs from the rostro-premaxilla to a lateralline pore posterior to the nostril. On the right side, asmall displaced piece of bone lying in the nostril open-ing could be a fragment of the missing right nasal 1.The rounded NASAL 2 lies lateral to the internasal andcarries the canal from the rostro-premaxillae to thenasals 3. NASAL 3 is roughly square and joins its anti-

Figure 3. Photograph and drawing of the skull of TM90-01-39, holotype of Polypterus faraou sp. nov., in dorsal view.

Figure 4. Photograph and drawing of the snout of TM90-01-39, holotype of Polypterus faraou sp. nov., in anterolateraldorsal view.

A NEW POLYPTERID FROM THE LATE MIOCENE OF CHAD 231

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mere at the midline. There are no internasal super-numerary plates (they develop frequently in someliving species, e.g. P. weeksii; Poll, 1942). The supraor-bital sensory canal of either side passes posteriorlythrough nasals 1, 2 and 3 to the frontals. The openingfrom the canal within nasal 3 lies within the posteriortwo-thirds of the bone.

On each side of the skull, the ROSTRO-PREMAXILLA

carries the infraorbital canal from the midline (inter-nasal) to the maxilla, via the lacrymal. It extendsbetween the nostril and the orbit, along the ventralmargin of nasal 3, and sutures posteriorly with thefrontal. The ascending process of the rostro-premax-illa is postero-ventrally covered by the LACRYMAL. Thelacrymal is a tubular bone that carries the infraorbitalcanal from the rostro-premaxilla to the maxilla. Thelacrymal shows a preorbital process dorsally. The MAX-

ILLA reaches from the level of the nostril to the pres-piracular series. The POSTORBITAL borders the back ofthe orbit from the maxilla to the frontal, along theleading edge of the prespiracular series. It is slightlycurved backwards in its caudal part, delimiting a freenarrow space with the lateral border of the frontal atthe postero-dorsal edge of the orbit. The infraorbitalcanal runs from the lacrymal to the postorbitalthrough the maxilla and to the frontal through thepostorbital. On this latter bone, there is a tiny dorsalopening whereas the ventral one, just above the max-illa, is wide.

Nasal 3 is the only bone of the snout with a dermalornamentation of distinctly separated tubercles cov-ered by ganoine. The other snout bones are smooth,ganoine-free and with numerous small pores particu-larly in the rostral part. Caniniform teeth are devel-oped on the ventral face of the rostro-premaxilla infront of the maxilla, and on the maxilla from the ante-rior tip to the midlevel of the orbits.

DORSAL SIDE OF THE HEAD (FIGS 3 AND 4)

The FRONTALS are the largest bones of the head. Thefrontal branch of the lateral canal has two openingsabove the orbit (only one is seen on the right side of thefossil). It connects with the infra-orbital branch infront of the spiracular bones, at the level of the der-mosphenotic. According to Jollie (1984), the canal isshared by both the frontal and the dermosphenotic atthat point, and there is an opening on the dermosphe-notic. Only the opening of the dermosphenotic can beseen, but not the limits of the bone itself. It seems to beabsent or totally incorporated in the frontal. At thepostero-lateral angle of each frontal, the canal passesto the INTERTEMPORO-SUPRATEMPORAL, where it opensin a pore midway along the length of the bone. Theintertemporo-supratemporal is roughly rectangularin shape. There are six EXTRASCAPULAR PLATES. Four

are aligned along the posterior border of the inter-temporo-supratemporals, and two are lateral. Thelast-mentionned are diamond-shaped, and they liebetween the post-spiracular bones, the more medialextrascapular plates and the posttemporal. There areopenings of the lateral line between the extrascapularplates and between the lateral extrascapular plateand the posttemporal. The POSTTEMPORAL is roughlyrectangular in shape and shows a posterior openingfor the lateral-line canal. The posterior process is notseen. It is probably broken on the left side where thescales are slightly displaced (it is present in livingPolypterus but hidden by the scales). The posteriormidline scale is missing.

The PRESPIRACULAR, SPIRACULAR and POSTSPIRACU-

LAR bones border the lateral edge of the former dorsalbones of the skull, from the postorbital to the posttem-poral, above the opercular series. The spiracularbones lie along the postero-lateral border of thefrontal and the lateral border of the intertemporo-supratemporal. The spiracular formulae are, respec-tively, 5–2−3 on the left side, and 7–2−4 on the right.The SPIRACLE opens along the second spiracular bone,above the DERMOHYAL, the dorsal face of which can beseen.

All of the skull roofing bones have a dermal orna-mentation of distinctly separated tubercles covered byganoine on their dorsal face.

ORBITOSPHENOID, ECTOPTERYGOID AND LATERAL ETHMOID (FIG. 4)

Parts of these three bones and their spatial relation-ships are seen in the left orbit of the specimen.

OPERCULAR SERIES AND CHEEK (FIG. 5)

The opercular series is well developed, with a largeSUBOPERCULUM the dorsal extremity of which reachesthe preorbital canal median opening, and an OPERCU-

LUM as large as the PREOPERCULUM. The posteroven-tral process of the preoperculum is present. TwoSUPERNUMERARY CHEEK PLATES lie anterior to theposteroventral process, along the preoperculum ven-tral border. Together with the process, they totallycover the cheek. Anteriorly, the preoperculum issutured with the maxilla. The preopercular sensorycanal has four openings. The first is dorsal and islocated between the spiracular and postspiracularseries. The second opening lies close to the posteriorborder of the bone at one-quarter of its height. Thethird is in a more ventral position, just above the ven-tral process of the preoperculum. The fourth openinglies at the lower extremity of the ventral process.

All of the cheek bones have their surface covered bythe ganoine tubercules.

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LOWER JAW AND GULAR AREA (FIG. 6)

The lower jaw is prognathus. The posterior level of thesuture between the DENTOSPLENIAL and the ANGULAR

reaches the anterior level of the supernumerary cheekplates. The angular–prearticular–articular sutures

are not seen, and nor is the quadrate–articular arti-culation; they are hidden by the gular and the cheeksupernumerary plates. The coronoids and mento-meckelian bones are not observable, owing to theirinternal position and small dimension. Caniniformteeth are developed on the edge of the dentosplenial.

Figure 5. Photograph and drawing of the opercular series and cheek of TM90-01-39, holotype of Polypterus faraou sp.nov., in laterodorsal view.

Figure 6. Photograph and drawing of the skull and pectoral girdle of TM90-01-39, holotype of Polypterus faraou sp.nov., in ventral view.

A NEW POLYPTERID FROM THE LATE MIOCENE OF CHAD 233

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Ventrally, the wide and long GULAR PLATES aremostly covered by a thin ganoin ornamentation exceptin their anteriormost parts. They cover nearly thewhole ventral surface between the lower jaws.Because they are slightly displaced, a medial bone isobservable which could be the urohyal.

PECTORAL GIRDLE AND BASE OF THE FINS (FIGS 6, 7)

The pectoral girdle is composed of stout bones. Dor-sally and posteriorly, the SUPRACLEITHRUM bordersthe operculum and it covers the first scale row. Later-ally, the POSTCLEITHRUM is probably represented by abony plate broken in three fragments. It is delicatelyornamented with smooth ganoine tubercles, and it islying above an aggregation of small scales which is thelateral edge of the base of the pectoral fin. Ventrally,the CLEITHRA join in the midline. They are coveredanteriorly by large clavicles that articulate with oneanother by two small processes and a notch.

SCALES AND FINLETS (FIG. 8), AXIAL SKELETON

There are 15 pinnules bearing the finlets. The firstinserts behind the 14th row of scales. Each pinnule isseparated from the following one by three scale rows.They are long enough to cover the base of the followingone when folded in life. The pair of scales with whicheach pinnule articulates are L-shaped. The distalextremity of each pinnule is forked and the articularbase is symmetrical. On one pinnule, at least two fin

rays can be seen. The caudal fin starts dorsally behindthe last finlet at the 48th scale row, and ventrally atthe 53rd scale row. The first six dorsal and first sevenventral caudal rays are preserved in their proximalpart. All scales have exposed surface covered byganoin. There are 23 scales on each transversal rowacross the body on either side: most of the scales of thelateral line bear a groove that opens posteriorly in anotch, and some present a simple pore. There are eightscales above and 14 below the lateral line in a trans-versal row. There are 58–60 longitudinal scales, andthus probably about 60 vertebrae (Daget & Desoutter,1983). This agrees with the count of centra madewhere the covering scales are displaced. The centraare typical, rounded with one median and two lateraldeep gutters ventral to the lateral apophysis.

PELVIC FIN (FIG. 9) AND ANAL FIN

The scaly base of the left pelvic fin and the proximalpart of the rays are preserved. The fin inserts behindthe 31st transversal row of scales. There are at least11 pelvic rays. The position of the anal fin is assumedbased on the preceding small square scales known inliving polypterids.

SYSTEMATIC AFFINITIES AND DISCUSSION

Polypterus faraou has a character unique to the cla-distians: the dorsal fin is composed of several finlets,each consisting of a pinnule articulated with one or

Figure 7. Photograph and drawing of the operculum, cleithrum and postcleithrum of TM90-01-39, holotype of Polypterusfaraou sp. nov., in lateral view.

Figure 8. Photograph and drawing of pinnules 1–4 in place with the surrounding scales of TM90-01-39, holotype ofPolypterus faraou sp. nov., in dorsal view.

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more soft rays. It also shows polypteriform character-istics such as absence of branchiostegals and a maxillathat carries the infraorbital sensory canal. It haspolypterid features: infraorbital canals fused to themaxilla and fusion of lateral rostral bones to the pre-maxilla (Pehrson, 1947; Jollie, 1984), the presence ofspiracular bones, the preoperculum covering the cheekand three separate nasal bones. The lateral-line sys-tem on the head of Polypterus faraou conforms to thecommon pattern described by Jollie (1984) for livingpolypterids.

Polypterus faraou has symmetrical pinnules as inRecent Polypterus species and in Erpetoichthys,whereas a different structure of the articular head ofthe pinnules characterized the fossil genera describedby Gayet & Meunier (1996) and Werner & Gayet(1997) (see Introduction). It also differs from Ser-enoichthys, in which the body is much shorter thanin Recent genera (Dutheil, 1999). However, it doesnot show the elongation of the body as observed inErpetoichthys, nor the reductive characters of thatgenus, e.g. no suboperculars and no supernumerarycheek plates (Smith, 1865; Poll, 1941b; O. Otero, pers.observ.). Moreover, at least one of the pinnule bears atleast two rays as in Recent Polypterus species, by con-trast with Erpetoichthys, the pinnules of which bearone single fin ray (Daget, 1950; O. Otero, pers. observ.).From this evidence, we assign the new species to thegenus Polypterus.

Poll (1941a, b, 1942, 1965) described the Recentpolypterid species and defined six anatomically basedclusters of species and subspecies organized on ana-tomical trends deriving from a central type (Fig. 10A).The possible phylogenetic significance of these clustershas not been established; they only have a descriptivevalue. Polypterus faraou belongs to the P. bichir –P. endlicheri cluster with: (1) head length about 20% ofbody length; (2) head depressed; (3) prognathus jaw; (4)opening of the lateral line on the nasal 3 close to its pos-terior border; (5) orbit length smaller than the subo-

perculum width; (6) successive pinnules overlappingthe base of the following ones when folded in life; (7)grooved lateral line scales with notched posterior mar-gin. It also has other characteristics observed inP. bichir, P. endlicheri and also in some other species:(1) superolateral position of the orbit (P. ansorgii,P. weeksii); (2) 5–7 prespiracular bones (P. ornatipin-nis, P. weeksii); (3) 15 finlets (P. ansorgii); (4) deep body,with 46 transversal scales and 58 scale rows(P. ornatipinnis, P. ansorgii, P. weeksii); (5) only 14 pre-dorsal scales (P. delhezi); (6) known maximum stan-dard length of 590 mm (P. ornatipinnis). Moreover,Polypterus faraou differs from P. bichir and resemblesP. endlicheri based on its depressed head, and largeand rounded snout which is shorter than the interor-bital distance; it differs from P. endlicheri and resem-bles P. bichir katangae based on its orbital length,which is 50% of the interorbital space in adults (lessthan 40% in adults of P. endlicheri subspecies andP. bichir subspecies bichir and lapradei). Finally,Polypterus faraou is also the only Polypterus specieswith such a wide head: the head width at the level ofthe preoperculum is about 70% of the length; this canalso be expressed by the distance between the lateralborders of the spiracular series (at the level of the pre-operculum), which is 45% of the head length whereasit is around one-third in large specimens of P. bichir.

In conclusion, the new taxon is assigned to thegenus Polypterus based on its morphological charac-teristics, which fall into the range observed in the spe-cies of the genus, particularly the cluster P. endlicheri– P. bichir, from which it differs by a unique combina-tion of characters. The suggestion that the clusterformed by P. faraou and the Recent P. endlicheri andP. bichir (Fig. 10A) is a natural group will need to betested as intrarelationships among Polypterus speciesare still unknown. Nevertheless, this hypothesis is inagreement with the distribution of extant species:among the three polypterid fishes living in the Chad–Chari system, P. endlicheri and P. bichir are present

Figure 9. Photograph and drawing of the left pelvic fin of TM90-01-39, holotype of Polypterus faraou sp. nov., in lateralview.

A NEW POLYPTERID FROM THE LATE MIOCENE OF CHAD 235

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(Fig. 10B), as represented by P. endlicheri endlicheriand P. bichir bichir; the third one is P. senegalus(Gosse, 1990). However, the phylogenetic relation-ships of Recent polypterids must be established beforewe can draw any biogeographical inferences. A cladis-tic analysis on the basis of anatomical characters willrequire further anatomical review of the species,which seem morphologically so close to each other anddiffer mainly in their combination of characteristics.Moreover, difficulty exists in choosing an outgroupbecause (1) the closely related Erpetoichthys must beincluded as an ingroup in such an analysis (this mono-typic genus is characterized by reductive charactersand the elongation of the body; it thus could be moreclosely related to one of the species of Polypterus), and(2) the related fossils are only known by their pinnulesand/or scales, except Serenoichthys (see Introduction).However, two anatomical characters have been dis-cussed previously in terms of primitive/derived states,

and for the first time they are both observed in a fossilattributed to the genus Polypterus:

1. The scales of the lateral line bear a groove thatopens posteriorly in a notch and this is regarded asa primitive state for polypteriforms. The derivedstate is thought to be lateral line pores piercing thebody of the scale. This assumption was made byPoll on the basis of ontogenetic arguments.P. faraou shows this character state, as do P. bichir,P. endlicheri and P. ansorgii.

2. A deep and short body (low vertebrae count) is aprimitive state for polypteriforms. This assumption(Daget & Desoutter, 1983) is congruent with thebody shape of the Cretaceous Serenoichthys (asnoted by Dutheil, 1999), and also with the generalobservations made on the elongation of the bodyamong actinopterygians. P. faraou has a short anddeep body with 46 scales in a transversal row, as

Figure 10. The Recent polypterid species and Polypterus faraou sp. nov. (A) Position of the species in the anatomicallybased clusters of species, as defined by Poll, P. teugelsi not included (see Britz, 2004, for discussion), and (B) distribution inthe African hydrographical basins; data from FishBase (Froese & Pauly, 2005) and map of the ichthyofaunic regions ofAfrica from Roberts (1975).

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in P. bichir, P. endlicheri, P. weeksii and P. ansorgii,and with fewer than 60 scales in a longitudinal row,as in all Recent species except P. ornatipinnis,P. bichir and Erpetoichthys. We can also considerthe trend to anguilliform shape through the posi-tion and the count of the dorsal finlets. On thisbasis, P. faraou has no anguilliform character, thenumber of pinnules being greater than 12, and thecount of predorsal scales being lower than 15 (as inP. bichir, P. endlicheri and P. ansorgii).

The polypterid from Toros-Menalla (westernDjurab, Chad) described here is the first fossil speci-men known by a near complete articulated skeletonincluding a cranium. It is assigned to the genusPolypterus and recognized as a new species, Polypterusfaraou. It is c. 7 Myr in age (Vignaud et al., 2002).

ACKNOWLEDGEMENTS

We thank the Chadian authorities (Ministère del’Education Nationale et de la Recherche, Universitéde N’Djaména, CNAR). For their support, we extendour gratitude to the French Ministère de l’Enseigne-ment supérieur, de la Recherche et de la Technologie(CNRS; Université de Poitiers) and the Ministèredes Affaires Etrangères (DCSUR, Paris; CoopérationSCAC, N’Djaména), to the Région Poitou-Charentesand the Département de la Vienne. The MPFT field-work is also supported by an NSF/RHOI Grant. Wethank Emmanuel Fara (CNRS, Poitiers) for discus-sion, the referees for their reviews and comments, andalso all members of the MPFT. Drawings and photo-graphs by Olga Otero.

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