Chromosomal evolution in prosimians

A cytogenetic study of almost all the Malagasy lemurs, of several representative Lorisiforms and one representative each of Tupaiiforms and Tarsiforms is reported. A phylogenic tree was constructed for all species exceptTarsius syrichta, which could not be related to either Prosimians or Simians. Three branches emerge, independentely or after a short common trunk, from the ancestral karyotype of all the Primates. One branch leads to the Lorisiforms, another to the Lemuriforms and the third to the Tupaïa. The chromosomal evolution of the Lorisiforms which gave rise to the Galagidae and the Lorisidae is of a populational mode, while among the Lemuriforms 4 modes of speciation have occurred: populational for the Indriidae, dichotomic for the Lepilemuridae, bushy for the Lemuridae and a catenary one for the Hapelemurs.