HISTOLOGICAL RECONSTRUCTION OF DENTAL DEVELOPMENT AND AGE AT DEATH INA JUVENILE GIBBON (HYLOBATES LAR)

Although research on dental development in great apes and modern human s has provided comparative models for life history, growth and develop ment in hominin evolution, almost nothing is known about dental develo pment in their sister group, the hylobatids. Hylobatids are of interes t because they differ in important life history variables from other c atarrhines of similar body mass, and can help to provide more general models for the factors underlying patterns of dental development. This study uses histological techniques to reconstruct developmental seque nce, crown formation times, root extension rates, daily rates of ename l and dentine formation, and age at death in a single specimen of Hylo bates lar. Thin sections were prepared of permanent mandibular teeth a nd analyzed by polarized light microscopy. Age at death was determined to be 2.88 yrs calibrated from a pattern of accentuated growth increm ents. At this age, permanent teeth in occlusion include I-1, I-2, and M-1. Developing permanent teeth include C-1, P-3, P-4, and M-2. P-3 la gs behind P-4 in development, and there is no indication of M-3 presen t in the crypt. Differences between the gibbon specimen and great apes include greater prenatal development of M-1, accelerated incisor deve lopment relative to molars and prenatal development of I-1, no overlap between M-2 and M-3 crown development, shorter crown formation times, and slower root extension rates of 4-5 mu m daily in the molars. Root extension rates are higher in the incisors. The periodicity of growth increments is four days, more similar to macaques than to other homin oids. Daily formation rates for enamel of 1.2-4.9 mu m and dentine of 1.7-4.9 mu m are similar to those reported for other catarrhines. (C) 1998 Academic Press.