It has been suggested that this oversight was made because Darwin only reported seeing tortoises on San Cristóbal (C. chathamensis) and Santiago (C. darwini), both of which have an intermediate type of shell shape and are not particularly morphologically distinct from each other.
Suxeriuse que esta neglixencia fíxose porque Darwin só informou que vira tartarugas en San Cristóbal (C. chathamensis) e Santiago (C. darwini), ambas as dúas de tipo intermedio en canto á forma da coiraza e non especialmente distintas morfoloxicamente entre si.