Ouranopithecus macedoniensis (Mammalia, Primates, Hominoidea): virtual reconstruction and 3D analysis of a juvenile mandibular dentition (RPl-82 and RPl-83) Roberto MACCHIARELLI Muséum national d’Histoire naturelle, Département de Préhistoire, UMR 7194 CNRS, 1 rue René Panhard, F-75013 Paris (France), and Université de Poitiers, Département Géosciences, 40 av. du Recteur Pineau, F-86000 Poitiers (France) [email protected] Arnaud MAZURIER Société Études Recherches Matériaux, CRI-BIOPOLE, 4 rue C. Heitz, F-86000 Poitiers (France) [email protected] Bernhard ILLERHAUS Federal Institute for Materials Research and Testing (BAM), Richard-Willstäatter-Str. 11, G-12478 Berlin (Germany) [email protected] Clément ZANOLLI Muséum national d’Histoire naturelle, Département de Préhistoire, UMR 7194 CNRS, 1 rue René Panhard, F-75013 Paris (France) [email protected] Macchiarelli R., Mazurier A., Illerhaus B. & Zanolli C. 2009 — Ouranopithecus macedonien- sis (Mammalia, Primates, Hominoidea): virtual reconstruction and 3D analysis of a juvenile mandibular dentition (RPl-82 and RPl-83). Geodiversitas 31 (4) : 851-863. ABSTRACT Dental enamel thickness is commonly listed among the diagnostic features for taxonomic assessment and phylogenetic reconstruction in the study of fossil homi nids, and is widely used as an indicator of dietary habits and palaeoen- KEY WORDS vironmental conditions. However, little quantitative information is currently Mammalia, Primates, available on its topographic variation in deciduous crowns of fossil primates. By Ouranopithecus, means of high-resolution microtomography, we investigated the inner structural hominid, Miocene ape, morphology of the mixed lower dentition of Ouranopithecus macedoniensis, a mixed dentition, late Miocene large-bodied ape from Macedonia, Greece. With respect to the microtomography, extant African apes and Homo, O. macedoniensis shows a signifi cant diff erence tooth inner structure, 3D reconstruction, in occlusal enamel thickness between the relatively thin deciduous second molar enamel thickness. and the absolutely thick-enamelled permanent fi rst molar. GEODIVERSITAS • 2009 • 31 (4) © Publications Scientifi ques du Muséum national d’Histoire naturelle, Paris. www.geodiversitas.com 851 Macchiarelli R. et al. RÉSUMÉ Ouranopithecus macedoniensis (Mammalia, Primates, Hominoidea) : reconstruction virtuelle et analyse 3D d’une denture inférieure juvénile (RPl-82 et RPl-83). L’épaisseur de l’émail dentaire est couramment incluse parmi les traits diagnos- tiques pour l’attribution taxinomique et la reconstruction phylogénétique dans l’étude des hominidés fossiles, et elle est aussi utilisée comme indicateur d’ha- bitudes alimentaires et de conditions paléoenvironnementales. Cependant, peu MOTS CLÉS d’informations quantitatives sont disponibles à ce jour concernant sa variation Mammalia, Primates, topographique dans les couronnes déciduales des primates fossiles. Grâce à la Ouranopithecus, microtomographie à haute résolution, nous avons exploré la morphologie struc- hominidé, Miocène, turale interne de la denture inférieure mixte d’Ouranopithecus macedoniensis, un denture mixte, grand singe du Miocène supérieur de Macédoine, Grèce. Par rapport aux grands microtomographie, singes africains actuels et à Homo, O. macedoniensis montre une diff érence signi- endostructure dentaire, reconstruction 3D, fi cative dans l’épaisseur de l’émail occlusal entre la deuxième molaire déciduale, épaisseur de l’émail. relativement fi ne, et la première molaire permanente, très épaisse. INTRODUCTION Th e individual, likely a male whose age at death has been estimated between 3.5 and 6 years (Kou- Ouranopithecus macedoniensis (Bonis & Melentis, fos & Bonis 2004), is represented by two fragments, 1977) is a late Miocene large-bodied ape currently RPl-82 (left partial ramus) and RPl-83 (right par- known from three localities in Macedonia, Greece: tial ramus). According to its original description, Ravin de la Pluie (RPl) and Xirochori (XIR), in the left fragment preserves in situ three erupted the valley of the Axios River, and Nikiti-1 (NKT), deciduous teeth, all in occlusion: the lateral in- in the Chalkidi peninsula, east of Th essaloniki cisor (Li2), the canine (Lc), and the fi rst molar (Bonis & Koufos 2001). Th e associated mam- (Lm1). On radiographic ground, the presence malian fauna, which globally indicates an open of the third premolar crown (LP3) has been also environment (Bonis et al. 1999; Merceron et al. reported (Koufos & Bonis 2004). On the larger 2005a, 2007), suggests a late Vallesian age (MN RPl-83 right fragment, the following deciduous 10). More precisely, the magnetostratigraphic record and permanent erupted elements are visible: the available for the two northern sites of the Axios deciduous canine (Rc), both deciduous molars valley indicates the interval 9.6-9.3 Ma (Sen et al. (Rm1 and Rm2), and the fully erupted, unworn 2000), while the faunal assemblage from Nikiti fi rst permanent molar (RM1). In addition, par- points to a slightly younger age, within the interval tially embedded in a hard matrix, the permanent 9.3-8.7 Ma (Koufos 2000). crowns of the permanent central incisor (RI1), of Firstly discovered in 1973 in the Axios valley both lateral incisors (LI2 and RI2), and of the ca- (Bonis et al. 1974), Ouranopithecus Bonis & Me- nine (RC) can be traced. On the same specimen, lentis, 1977 is currently represented by cranial the presence of both permanent premolars (RP3 and mandibular remains and, mostly, from a large and RP4) has been recorded through radiography sample of isolated permanent teeth (Bonis et al. and cross-sectional computed tomography images 1975, 1990, 1998; Koufos 1993, 1995; Bonis & (Koufos & Bonis 2004). Koufos 1993; Koufos & Bonis 2006). Th e man- Specimens bearing a mixed dentition are rare in dibular remains of a young individual from the c. the non-human hominid and, to a lesser extent, 9.3 Ma site of Ravin de la Pluie, bearing a partial hominin fossil record (see review in Hartwig 2002; mixed dentition, have been discovered for the fi rst Schwartz & Tattersall 2005; for the largest sample time in 2001 and reported in 2004 (Koufos & of deciduous teeth for any species of fossil ape, see Bonis 2004). Mortzou & Andrews 2008), and the information 852 GEODIVERSITAS • 2009 • 31 (4) Ouranopithecus virtual dentition currently available on dental inner structural or- (Mercury Computer Systems Inc.) and Artecore ganization, including tissue proportions and enamel v.1.0 (Nespos Society). Th reshold values between thickness topographic variation of fossil primate taxa segmented components were found according to mostly concerns permanent teeth (see Olejniczak the methodology of Spoor et al. (1993). et al. 2008a, b). Th e assessment of the relative developmental Here we present preliminary evidence on the struc- stages of RPL-82 and RPL-83 deciduous and per- tural morphology of deciduous and permanent front manent dental elements are based on the scoring and cheek crowns of Ouranopithecus macedoniensis systems established by Demirjian et al. (1973) and based on the three-dimensional (3D) reconstruc- by Liversidge and Molleson (2004), recently revised tion and quantitative analysis of the high-resolution and integrated by Bayle et al. (2009a). microtomographic record of the two mandibular For individual measurements, crowns were digit- portions from Ravin de la Pluie (Koufos & Bonis ally isolated from roots following Olejniczak et al. 2004). More specifi cally, we comparatively assess (2008c), and surface rendering was performed using enamel thickness topography and proportions in its triangulation and constrained smoothing from the second deciduous and fi rst permanent molars. volumetric data (Lorensen & Cline 1987). In the case of the right deciduous second molar (Rm2) and of the permanent fi rst molar (RM1), enamel METHODS thickness variation was assessed on the buccolingual (BL) mesial section through metaconid-protoconid Th e microtomographic (μCT) acquisition and (BLm), the BL distal section through entoconid- reconstruction of RPL-82 and RPL-83 have been hypoconid (BLd), the mesiodistal (MD) lingual performed in 2002 at the Bundesanstalt für Material- section through metaconid-entoconid (MDl), forschung und -prüfung (BAM) of Berlin (http:// and the MD buccal section through protoconid- www.ct.bam.de/). A high-resolution 3D-tomograph hypoconid (MDb) (see Macchiarelli et al. 2004). equipped with a unique bipolar 320 kV micro fo- Th e following linear, surface, and volumetric vari- cal X-ray tube combined with a fl at panel detector ables have been measured on 2-3D reconstructions: of 1024 × 1024 pixels has been used. Scans para- total crown surface area; surface area of the enamel- meters were as follow: 240 kV tube voltage; 0.05 dentine junction (EDJ); volume of the enamel mA tube current; 0.25 mm Sn V-fi lter; 1200 (each cap; volume of the coronal dentine (including the 0.3°) and 900 (each 0.4°) respectively for RPL-82 coronal aspect of the pulp chamber); average enamel and RPL83. Reconstructions of the fi nal volumes thickness (AET; total volume of the enamel/EDJ (isotropic voxel size of 50 μm) have been done with surface area); average of minimum enamel thick- Advanced Visualization Software v6.1 (AVS, Inc.). ness (average of the minimum thickness between Virtual cross-sections 3D rendering were done at each outer enamel surface element and all the ERM, Poitiers (http://www.erm-poitiers.fr) by elements representing the EDJ); maximum radial means