KroeberAnthropological Society Papers, Nos. 71-72, 1990 Morphology and Metrics of the Upper Third Molars of Australopithecus afarensis Pelaji S. Kyauka This paper presents comparative data for the upper third molars attributed to Austrlopithecus afarensis from the sites of Laetoli and Hadar. The analysis is based on morphological and metric characters. The metric data show that specimens AL. 200-la and AL. 333x-1 are more similar to each other than they are to the other known upper third molars of A. afarensis. Morphologically, the upper third molars of A. afarensisfrom Laetoli and Hadar are similar in many of thefeatures compared. This observation sug- gests that the Laetoli and Hadar specimens attributed to A. afarensis are not heterospecific. INTRODUCTION Morphological and metrc studies of the den- tal characteristics of Australopithecus afarensis can provide vital data for clarifying its integrity and relationship with other hominid species. Al- though studies of this nature are important, few attempts have been made (see White 1985; Leonard and Hegman 1987; Cole and Smith 1987). The naming of Australopithecus afarensis as a new taxon by Johanson et al. (1978) included the pooling of specimens from Laetoli and Hadar. A number of researchers, including Tobias (1980), questioned this rationale. Tuttle (198 la, 1981b, 1985, 1987), for instance, doubted the possibility that a creature resembling A. afarensis from Hadar made the footprints found at Laetoli. Furthermore, some questions have been raised on whether the specimens attributed to A. afarensis from Hadar represent one species or more than one species (see, for example, Coppens 1977, 1980, 1981, 1983; Ferguson 1983, 1984; Her- bert 1983; Leakey 1981a, 1981b; Olson 1985; Senut and Tardieu 1985; Tardieu 1986; Zihlman 1985). However, others (e.g., Blumenberg and Lloyd 1983; Leonard and Hegman 1987; White 1985; White and Suwa 1987) have shown that the single species argument for the Hadar homi- nid fossils and the pooling of the Laetoli and Hadar specimens are justified. For more than ten years, then, the integrity of A. afarensis has been a subject of continuous and vigorous debate. The debate is not yet over (Ferguson 1989). The present paper uses the general morphological and metric features of the upper third molars attribu- ted toA. afarensis known from Hadar and Laetoli as a further attempt to resolve this controversy. MATERIALS AND METHODS A comparison of morphological and metric characters of the upper third molars of Australo- pithecus afarensis specimens recovered from Laetoli, Tanzania and Hadar, Ethiopia is given. Morphological descriptions are based on termi- nologies and techniques used by Grine (1984), White (1977, 1980), Biggerstaff (1969) and Jo- hanson et al. (1982). Metric and morphological comparisons were made using published data and observations of the casts of fossils A.L. 199-1, A.L. 200-la, A.L. 333x-1, A.L. 161-40 and A.L. 388-1 from Ethiopia, and L.H. 5, L.H. 12, L.H. 8(b) and Garusi II from Laetoli, Tanzania. MORPHOLOGICAL ANALYSIS Occlusal View The occlusal surface outline of Garusi II, like that of A.L. 200-la (right and left), A.L. 333x-1, L.H. 5, A.L. 199-1 and A.L. 161-40, is a round angled rhomboid, unlike that of L.H. 8(b), which is more circular. The outline of the occlusal view of the basal area of A.L. 199-1 and Garusi II is rhomboidal, while that of A.L. 200- la, A.L. 333x-1, A.L. 161-40, L.H. 8(b) and L.H. 5 is heart-shaped or triangular, with mesi- ally placed apices, distally placed hypotenuses and lingually placed bases. The distocclusal groove of L.H. 5 runs almost parallel to the distal marginal ridge. The distocclusal grooves of A.L. 200-la (right and left), A.L. 333x-1 and A.L. 161-40 run distally on the occlusal surface until they intercept the median longitudinal groove, distobuccal foveal groove and the distolingual foveal groove at the posterior fovea. The A.L. 200-la (left) and A.L. 161-40 dis- tobuccal cusps are incised into two cusps, and the area between the cusps of A.L. 161-40 is pitted. The right A.L. 200-la metacone is notched into five cusps while those of A.L. 199-1 and A.L. 388-1 are notched into three and four cusps, res- pectively, by their distobuccal foveal grooves. 36 The A.L. 388-1 metacone has three cusps which are not formed by the distobuccal foveal groove. The distal trigon crest of A.L. 333x-1, like that of A.L. 161-40, A.L. 200-la and A.L. 199- 1, is well-developed and notched by the median longitudinal groove. A well-developed plagio- conule is formed on the lingual side of the distal trigon crests of A.L. 200-la and A.L. 199-1. Due to wear, the presence of a plagioconule on L.H. 5, Garusi II and L.H. 8(b) cannot be deter- mined. The anterior fovea of A.L. 161-40 is a straight fissure placed on the mesial side of the paracone. It is bordered by the mesial marginal ridge and the epicrista on its mesial and distal sides, respectively. A.L. 200-la has an S- shaped broad and deep anterior fovea which runs along the marginal ridge with the epicrista on its distal side. A.L. 199-1 has a pit-like anterior fo- vea placed at the midline of the distal side of the mesial marginal ridge with no epicrista on its dis- tal side. The anterior fovea is not well-developed on A.L. 333x-1. The median longitudinal groove of A.L. 161-40, like that of A.L. 200-la (right and left) and A.L. 199-1, appears to begin at the distal side of the epicrista. It crosses the trigon crest and ends at the posterior fovea. The median longitudinal groove of A.L. 333x-1 seems to start directly at the edge of the mesial marginal ridge. Secondary crenulations are minimal on L.H. 5, A.L. 199-1 and A.L. 161-40, but prominent on A.L. 200-la, A.L. 333x-1 and L.H. 12. Be- cause of wear, it is difficult to assess the extent of secondary fissuration on Garusi II and L.H. 8(b). Lingual View The lingual surfaces of A.L. 200-la (left) and L.H. 5 have a lingual groove which shows a slight distal curvature. A.L. 200-la (right), A.L. 161-40 and A.L. 333x-1 have lingual grooves which are straight and inclined distocclusally. Unlike L.H. 5, the lingual grooves of A.L. 200- la, A.L. 161-40 and A.L. 333x-1 form wide V- shaped grooves as they cross the lingual marginal ridge. The lingual surface of Garusi II shows a slight concavity, especially close to the lingual marginal ridge. The A.L. 200-la, A.L. 333x-1, A.L. 199-1 and A.L. 161-40 lingual surfaces are slightly bilobed by the lingual groove, while L.H. 5 and L.H. 8(b) are relatively convex and flat, respectively. The cervical lines of A.L. 199- 1, Garusi II and L.H. 5 bulge upwards on the lingual surfaces while they are relatively straight on L.H. 8(b), A.L. 333x-1, A.L. 200-la and A.L. 161-40. The lingual surface of the A.L. 333x-1 protocone is heavily crenulated. Buccal View The paracones of Garusi II, L.H. 12, L.H. 8(b), A.L. 333x-1, A.L. 200-la, A.L. 199-1, A.L. 161-40 and probably L.H. 5 protrude buccally more than the metacone. The buccal marginal ridge of A.L. 199-1, A.L. 200-la, A.L. 388-1, A.L. 333x-1, A.L. 161-40 and Garusi II is notched by the buccal groove which continues down the buccal surface as a shallow depression. A.L. 200-la (right), like A.L. 199-1, A.L. 161- 40, L.H. 8(b), Garusi II, L.H. 5 and A.L. 388-1, has a cervical line which projects between the two buccal roots, whereas that of A.L. 200- la (left) is a straight line. The buccal surfaces of the A.L. 161-40, A.L. 200-la, A.L. 333x-1 and A.L. 199-1 metacones have shallow grooves which run on the surface from the cervical line to the buccal marginal ridge. Mesial View The mesial cervical line of A.L. 200-la, A.L. 388-1, A.L. 161-40, A.L. 199-1, L.H. 5, Table 1. Metrical dimensions of maxillary permanent dtird molars of Australopithecus afarensis. SPECIMEN A.L. 199-1 A.L. 200-la A.L. 333x-1 L.H. 5 A.L. 161-40 Garusi II BL 13.11 15.11 15.51 13.42 13.41 13.83 MD 11.41 14.31 13.61 10.92 11.81 10.93 BL x MD 149.34 215.93 209.25 146.06 158.12 150.42 BL+MD/2 12.25 14.70 14.50 12.15 12.60 12.35 BL/MD x 100 114.912 105.559 113.971 122.936 113.559 126.606 lJohanson et al. (1982) 2White (1980) 3Protsch (1981) 37 Garusi II and L.H. 8(b) is relatively straight. It projects between the buccal and lingual roots of A.L. 333x-1. The mesial surfaces of A.L. 200- la, A.L. 333x-1, A.L. 388-1, A.L. 199-1, L.H. 5, A.L. 161-40, L.H. 8(b) and Garusi II flare mesiocclusally with a slight concavity cervically. Distal View The distal surface of L.H. 8(b) bulges out- wards and is slightly bilobed, with a slight groove which is continuous with the median lon- gitudinal groove. The distal surface of Garusi II is almost straight but the hypocone bulges more distally. The distal surfaces of A.L. 333x-1, L.H. 5, A.L. 161-40 and A.L. 200-la are con- vex. Garusi II, L.H. 5, A.L. 161-40, A.L. 200-la and A.L. 199-1 have straight cervical lines. Although the cervical lines are straight for A.L. 333x-1 and L.H. 8(b), they are obliquely placed with the lowest part being on the meta- cone. METRIC ANALYSIS The crown sizes and shape measurements (Table 1) indicate that A.L. 200-la and A.L. 333x-1 have the largest buccolingual and mesio- distal dimensions. This is also true for the crown area and crown module which are measures of average crown dimensions and robusticity of the tooth, respectively. However, the crown shape index, an expression of the crown as a ratio of mesiodistal breadth to buccolingual length, is lar- gest for L.H. 5, while A.L. 200-la and A.L. 333x-1 have the lowest values. DISCUSSION This study adds significant information to our knowledge of Australopithecus afarensis. A bivariate analysis (Figure 1) indicates that A.L. 199-1, A.L. 161-40, Garusi II and L.H. 5 are closer to each other than they are to A.L. 200-la and A.L. 333x-1. However, due to the small sample size, interpretation of this observation must proceed with caution. It appears that an ap- propriate interpretation of this analysis must rely mostly on morphological characters. This seems reasonable since, despite the small sample size, more morphological characters (Figure 2) are compared than has been done previously. Out of the eighteen morphological features (Figure 2, A-R) analyzed, none of them separate the Hadar specimens from the Laetoli specimens. Apart from a wider V-shaped notch on the lingual marginal ridges of A.L. 200-la and A.L. 333x-1, and the S-shaped anterior fovea of A.L. 200-la, there are no specific morphological characters which differentiate the upper third molars of A. afarensis recovered from Laetoli from those re- covered at Hadar. In most instances, the majority of features are shared in both the Hadar and the Laetoli specimens (Figure 2). For example, A.L. Figure 1. Bivariate Plot of B/L Breadth x M/D Length in mm. 15 - 14 - 13 - 12 - 11 101 14 Buccal-Lingual 15 16 a Al.200-1 A.L. 333x-1 U * A.L. 16140 U A.L. 199-1 a U Gasill LH. 5 I 5 7; 4no rA 000 0 1 go 117 4) x 3 Figure 2. Comparisons of morphological characters. LHi 8(b) A Pa protruding more than metacone L.K 12 A L 333x-1 _ B Marl ridge notched by buccal groove Gamusi II A.LMla C Cervical line projecting between buccal roots A.L 16140 A.L 388-1_ LIL 8(b) | LH. S | D Curved lingual groove AL- 200- a (Left). A.L 200-la (Right) E V-shaped lingual groove Al.. 161-40 AL. 333x-l F Straight line lingual groove AL. 333x-1 G Convex disal surface L.H. 5 AL. 16140 H Staight cervical line AL. 200- la Garusi II AL. 199-1 A12.M la I Straight mesial cavical line A.L. 388-1 A.L. 161-40 A.L. 199-1 GaNsi II _ J Mesial surface flaring occlusally LH. 8(b) K Relatively straight lingual cevical line I L Lingual surface biobed M Lingual cervical line bulging upwards 38 39 Figure 2, continued. N Heia-shaped basal area oudine 0 Round angled rhomboid occiusal oudline P Rhomboid basal area outline Q Secondary crnuladons minimal R Secondary crenulations prominent 200-la, A.L. 333x-1, A.L. 161-40, Garusi II, A.L. 199-1 and L.H. 5 share a rhomboidal occlu- sal surface outline. The outline of the occlusal view of A.L. 199-1 is rhomboidal, like that of Garusi II, while that of A.L. 200-la, A.L. 333x- 1, A.L. 161-40, L.H. 8(b) and L.H. 5 is heart- shaped. Although minor morphological differences are apparent between the Hadar and Laetoli spe- cimens, most likely they represent individual variation. This claim is strengthened by the fact that the maxillary third molars in Homo sapiens are known to vary more than any other maxillary tooth in both shape and size (Brand and Isselhard 1982). The chances that the differences are within the range of variation of a single species are hence very high. However, unless more spe- cimens are found, the controversies will probably continue. 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