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186 A. D. BEYNON ET AL. Table 3 Comparative data for stria angles and stria widths in M1 only Taxon n Occlusal striae angles at EDJ Mean1 S.D. Lateral striae angles at EDL Mean1 S.D. Cervical striae angles at EDJ Mean1 S.D. Homo sapiens 20 13·01·5 27·02·6 32·0 1·8 Pan troglodytes 23 9·01·8** 26·06·0 31·0 4·3 Pongo pygmaeus 10 9·03·7* 30·07·1 41·0 5·6** Gorilla gorilla 28 7·03·1** 23·06·8* 31·010·7 Proconsul heseloni 1/2 12–28 18–21 28–45 Proconsul nyanzae 1 16 21–30 65–70 Occlusal striae widths at surface Mean1 S.D. Lateral striae widths at surface Mean1 S.D. Cervical striae widths at surface Mean1 S.D. Homo sapiens 20 37·02·8 28·03·2 21·0 3·5 Pan troglodytes 21 28·01·6** 27·02·1 20·0 2·7 Pongo pygmaeus 10 54·03·2** 47·07·7** 30·0 4·7** Gorilla gorilla 28 42·05·0** 33·05·3** 27·0 4·6** Proconsul heseloni 1/2 46 32–41 26 Proconsul nyanzae 1 28 25 Significance with respect to Homo; *P
DENTAL DEVELOPMENT IN PROCONSUL 187 Figure 11. ‘‘S-shaped’’ striae in the cervical enamel of the P. nyanzae M 2 (left) and the P. heseloni M 1 (right). (Individual IV) they measured 25 μm apart maximally. In the high cusped M 1 germ (Individual IV) 16·7 μm apart maximally, and in other lower crowned premolars and molars (Individual III) they measured on average 12·5 μm apart. Given that there is a five day periodicity between enamel striae in this individual, this implies daily rates of dentine formation were close to 5 μm per day in the I 1 , 3·3 μm per day in the high cusped M 1 and 2·5 μm per day in the other posterior teeth. Both in these teeth and others, daily lines with this expected periodicity in this position were measured (Table 4). This enabled mean daily rates of dentine formation in the cusps of several teeth to be estimated specifically for each tooth. Two deciduous teeth, the dm 1 and the dm 2 (Individual IV) had measurable daily lines in the coronal dentine of around 3·5 μm. Measurements made through the whole thickness of the cuspal dentine in two P. heseloni teeth (M 2 and M 3 ), demonstrated that there was a constant rate of dentine formation in the axis of cusps, as has been demonstrated in apes and humans (Dean & Scandrett, 1995). The mean value (n=23) for spacings of daily lines made on the photomontage of the M 2 was 2·4 μm (S.D.=0·21, range=1·95–2·66). For the M 3 (n=14) the mean value was 2·09 μm
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