CRANIAL ALLOMETRY AND GEOGRAPHIC-VARIATION IN SLOW LORISES (NYCTICEBUS)

A series of 20 craniodental measurements was obtained for two sister t axa: Nycticebus coucang (common slow loris) and N. pygmaeus (pygmy slo w loris). Multivariate analysis of variance was performed with adult d ata to describe patterns of subspecific and specific variation in this genus. The geometric mean of adult cranial dimensions was compared to field data on latitudinal coordinates for available specimens to inve stigate if size variation in Nycticebus is clinal in nature. Ontogenet ic series for larger-bodied N. coucang and smaller-bodied N. pygmaeus were compared to test the hypothesis that species and subspecific vari ation in skull form results from the differential extension of common patterns of relative growth. A MANOVA provides independent support of Groves's [pp. 44-53 in Proceedings of the Third International Congress on Primatology, Vol. 1 (Basel: S. Karger), 1971] classification of Ny cticebus into two species, with four subspecies in the common slow lor is and one form of the pygmy slow loris. Within N, coucang, cranial pr oportions for all four subspecies are ontogenetically scaled, and size differentiation is mainly clinal (Bergmann's Rule). N. c. bengalensis represents the most northerly disposed and the largest form. N. c. ja vanicus represents the next-largest form and is located in a southerly direction the next-farthest away from the equator. N. c. coucang and N. c. menagensis are both equatorial; however, the latter subspecies i s the smallest. A genetic basis for some of the taxonomic variation be tween N. c. coucang and N. c, menagensis is supported by such nonclina l variation in body size. Variation in the presence/absence of I-2 is not size-related but rather tracks geographic proximity and isolating factors which predate the most recent inundation of the Sunda Shelf. A lthough they inhabit a nonequatorial environment, pygmy slow lorises a re the smallest of all Nycticebus. As N. pygmaeus is sympatric with N. c.