Maturation of the Teeth and Skeleton of Kmnwt Basic Observations

To review briefly, the Nariokotome juvenile is judged to be male on the basis of sciatic notch morphology, skull robust-icity, and overall size of the skeleton (Ruff and Walker, 1993). KNM-WT 15000 certainly died at early adolescence, before reaching adult size and proportion of the axial and appendicular skeletons; further he had most likely initiated, but not completed, physical and behavioral sexual maturation (Table 9.7 in Smith, 1993). Major ossification centers of long bone epiphyses had appeared and most remained unfused; of note, the triradiate cartilage still separated primary elements of the innominate. Epiphyses of the distal humerus had begun to fuse (see below, and Smith, 1993;

F.E. Grine et al. (eds.), The First Humans: Origin and Early Evolution of the Genus Homo, Vertebrate Paleobiology and Paleoanthropology, © Springer Science + Business Media B.V. 2009

Fig. 10.1 The teeth and jaws of KNM-WT 15000. a), the recently erupted second permanent molars, premolars and lower canine are viewed laterally. The upper third molar region is broken away on this side (although the unerupted crown is preserved on the opposite side). b), the oblique view shows permanent upper and lower incisors; the permanent canine is erupted in the mandible, but the deciduous canine was still present in the maxilla.

Fig. 10.1 The teeth and jaws of KNM-WT 15000. a), the recently erupted second permanent molars, premolars and lower canine are viewed laterally. The upper third molar region is broken away on this side (although the unerupted crown is preserved on the opposite side). b), the oblique view shows permanent upper and lower incisors; the permanent canine is erupted in the mandible, but the deciduous canine was still present in the maxilla.

Permanent Dentition Outline

Fig. 10.2 The isolated teeth of KNM-WT 15000 drawn from sharp casts (a) and from radiographs (b). Dotted outlines project remaining growth. The drawing of the second radiograph shows it was taken in oblique view, which elongates the true tooth lengths (Reproduced from Smith, 1993. With permission of the editors and Harvard University Press).

Walker and Leakey, 1993). In the dentition, 26 permanent teeth had emerged, all but third molars and upper canines (Figs. 10.1 and 10.2).

The two deciduous upper canines remained in place. While the right upper third molar was never recovered, the upper left third molar crown can be observed through a window in the bone. There is no sign of either of the lower M3s on the best available radiographs (Brown and Walker, 1993); these had apparently failed to form. Wear on teeth suggests that upper and lower second molars had been in functional occlusion for a short time, and that the lower canines were probably the last teeth to erupt before death. Roots of most teeth (I2, I2, C, P3, P4 and M2) were incompletely formed at death, and the upper third molar crown was unerupted and probably incomplete.

Fig. 10.2 The isolated teeth of KNM-WT 15000 drawn from sharp casts (a) and from radiographs (b). Dotted outlines project remaining growth. The drawing of the second radiograph shows it was taken in oblique view, which elongates the true tooth lengths (Reproduced from Smith, 1993. With permission of the editors and Harvard University Press).

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