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The first reciprocal chromosome painting of lorisoids and humans show a remarkable syntenic homology between Otolemur and Nycticebus. Eight derived syntenic associations of human segments are common to both, indicative of a considerable period of common evolution between the greater galago and the slow loris.

We employed in situ hybridization of chromosome-specific DNA probes ('chromosome painting') of all human chromosomes to establish homologies between the human and the silvered lead monkey karyotypes (Presbytis cristata 2n=44). The 24 human paints gave 30 signals on the haploid female chromosome set and 34 signals on the haploid male chromosome set. This difference is due to a reciprocal translocation between the Y and an autosome homologous to human chromosome 5. This Y/autosome reciprocal translocation which is unique among catarrhine primates has produced a [X.sub.1][X.sub.2][Y.sub.1][Y.sub.2]/[X.sub.1][X.sub.1][X.sub.2][X.sub.2] sex-chromosome system. Although most human syntenic groups have been maintained in the silvered leaf monkey chromosomes homologous to human chromosomes 14 and 15, 21 and 22 have experienced Robertsonian fusions. Further, the multiple FISH signals provided by libraries to human chromosomes 1/9, 6/16 indicate that these chromosomes have been split by reciprocal translocations. G-banding analysis shows three different forms of chromosome 1 ([X.sub.2]) which differ by a complex series of inversions in the 10 individuals karyotyped. Comparisons with the hybridization patterns in hylobatids (gibbons and siamang) demonstrate that resemblances in chromosomal morphology and banding previously taken to indicate a special phylogenetic relationship between gibbons and colobines are due to convergence. KEY WORDS Presbytis cristata; catarrhine; primate; chromosome painting; polymorphism; evolution; speciation

The existence of an apomorphic reciprocal chromosomal translocation in the gorilla lineage has been asserted or denied by various cytogeneticists. We employed a new molecular cytogenetic strategy (chromosomal in situ suppression hybridization) combined with high-resolution banding, replication sequence analysis, and fluorochrome staining to demonstrate that a reciprocal translocation between ancestral chromosomes homologous to human chromosome 5 and 17 has indeed occurred.

Research has revealed that the Nasalis is nested within Asian colobines and shares a period of common descent with other colobines after divergence of pygathrix. Results confirm that the diploid number larvatus is unique among colobines