The genus Lepilemur was initially thought to comprise only 2 species: L. mustelinus and L. ruficaudatus, with the latter subdivided into 2 subspecies. The genus was later reclassified as having only 1 species, mustelinus, with 5 subspecies. In 1977, Petter et al. increased the species number of the genus to 7, at which point the species L. septentrionalis was demarcated, and classified as having 4 subspecies. As 2 of these subspecies were not geographically distinct, the number of L. septentrionalis subspecies was eventually condensed to 2: L. s. septentrionalis and L. s. ankaranensis. As a result of subsequent cytogenetic and molecular analyses, the 7 species of Lepilemur were confirmed by Rumpler et al. , but the L. s. ankarensis subspecies was elevated to the status of full species, resulting in 8 species of lemur classified within the genus. A further three molecular genetic studies have led to the inclusion of another 15 species of Lepilemur, making it the most diverse lemur genus at 23 species. In 2004, a study of the evolutionary relationships of various subpopulations of the northern sportive lemur was carried out, in which sequence analyses of the mitochondrial DNA of a large number of L. septentrionalis individuals from the different subpopulations were performed. A significant number of fixed differences present in the lemurs in the Sahafary region distinguished them from the lemurs in other regions, suggesting that the northern sportive lemur in fact exists as two separate cryptic species, most likely caused by chromosomal rearrangements in one of the L. septentrionalis evolutionary lineages.