| Summary: | We performed a molecular and phylogenetic analysis and a comparative cytogenetic study with standard karyotyping, silver staining (Ag-NOR) and sequential C-banding + Giemsa, + fluorochromes on several <i>Blaesodactylus</i> samples. The phylogenetic inference retrieved two main clades, the first comprises <i>B. victori</i>, <i>B. microtuberculatus</i> and <i>B. boivini</i>, while the second includes <i>B. sakalava</i>, <i>B. antongilensis</i> and <i>B. ambonihazo</i>. The available samples of <i>B. sakalava</i> form two different clades (here named <i>B. sakalava</i> clade A and clade B), which probably deserve a taxonomic re-evaluation. We found a karyological variability in <i>Blaesodactylus</i> in terms of chromosome number (2n = 40–42), morphology, location of NORs, and heterochromatin distribution pattern. <i>Blaesodactylus antongilensis</i> and <i>B. sakalava</i> clade A and B showed a karyotype of 2n = 40 mostly telocentric chromosomes. Pairs 1 and 6 were metacentric in <i>B. sakalava</i> clade A and B, while pair 1 was composed of subtelocentric/submetacentric elements in <i>B. antongilensis.</i> In contrast, <i>B. boivini</i> displayed a karyotype with 2n = 42 only telocentric chromosomes. NORs were on the first chromosome pair in <i>B. boivini</i>, and on the second pair in <i>B. antongilensis</i>. Adding our data to those available from the literature on evolutionarily related species, we highlight that the chromosome diversification in the genus probably proceeded towards a progressive reduction in the chromosome number and the formation of metacentric elements.
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