Subgenus Ctenosta Motschulsky, 1866
Ctenosta Motschulsky, 1866: 306 (type senegalense Dejean, 1831)
Eucalosoma Breuning, 1927: 181 (type grandidieri Maindron, 1900)
Epipara Lapouge, 1929: 3 (type grandidieri Maindron, 1900)
Paractenosta Jeannel, 1940: 123 (type guineense Imhoff, 1843)
The species belonging to Ctenosta are distinct from other species of the phyletic line Castrida - Caminara (sensu Jeannel, 1940) for the loss of the basal seta that in the others exists close to hind angles of the pronotum.
In all species of the subgenus Ctenosta, invariably, the hind angles of the pronotum are quite obliterated and the sculpture of elytra is characterized by 16 intervals on each of them; that means having a single tertiary interval on the sides of a secondary one ("triploïde" type). Also all the intervals are always distinctly separated by the striae.
The subgenus Ctenosta has a characteristic Indo-African spreading, already detected and discussed by Jeannel (1940; 1961) from the biogeographic point of view. In fact Ctenosta is specific to Africa including the island of Madagascar, where there are two endemic species, but it is also present in the Indian peninsula where we find another endemic species. This distribution seems consistent with the hypothesis of a differentiation before the separation of India from the African continent. This hypothesis has been advanced by Jeannel (1961: 20) for some groups of Carabidae with a similar distribution but it is undermined by the results of recent genetic studies (Su et Al., 2005) that seem to indicate that the origin of Calosomatina is much more recent than what had been previously hypothesized.
Moreover Jeannel (1940) had considered near to Ctenosta, Aplothorax burchelli Waterhouse 1842 from island of St. Helena, as a phylogenetically related species. On the contrary, according to Basilewsky (1972) it would be a quite distinct entity that should be attributed to a specific tribe (Aplothoracini), based on the larval morphology. Lastly Aplothorax burchelli was placed again as a separate genus inside of the subtribe Calosomatina, by reverting to the primacy of the phylogenetic considerations (Prüser and Mossakowski 1998: 300).