 Another 5 species are classified in the genus "Stenaria"; "Houstonia" without "Stenaria" is paraphyletic.Close relatives of the genus are "Oldenlandia microtheca" and, more distantly, "Arcytophyllum".Its members superficially resembles species of the genus "Myosotis" (Forget-me-nots), but are distinguished from the latter by having only 4 sepals (petals) instead of 5.