A total of 745 Fabaceae species-516 Faboideae, 192 Caesalpinioideae, 21 Detarioideae, 14 Cercidoideae and 2 Dialioideae species-, that inhabit Indian Western Ghats region, were characterized for their leaf lamina morphology. In all 16 leaf lamina types were identified, 12 of which are known and genetically understood in the model Faboideae Fabaceae species Pisum sativum and Medicago truncatula. Among the 16 leaf types, 5 were of simple type, 6 of unipinnate imparipinnate type, 2 of unipinnate paripinnate type, 2 of bipinnate paripinnate type and 1 of bipinnate imparipinnate type. Unifoliate leaves in Faboideae species were either in the form a simple tendril or a simple pinna. None of the Faboideae-species of tree habit was observed to produce unifoliate leaves. There were no herb species in other subfamilies that formed unifoliate leaves. Faboideae species bearing bipinnate leaves were absent. In Caesalpinioideae, different species produced all the 4 types of compound leaves. Cercidoideae and Detarioideae species were observed to bear largely unifoliate or bifoliate compound leaves. Simple pinnae in Cercidoideae and Detarioideae differed from those in Faboideae by having multiple primary veins. All leaf types were assigned pathway of origin. Whereas it is known that types leaf evolved from unipinnate imparipinnate leaf in Faboideae, it is suggested that unifoliate leaves in Cercidiodeae and Mimosoideae evolved from bipinnate paripinnate leaf types genotypes or vice versa. Evidence was found in favour of monophyletic origin followed by divergence in the genetic mechanisms, in the evolutionary process of leaf lamina architectural polymorphism in Fabaceae. Several directions of new research on the genetics of leaflamina morphogenesis in Fabaceae were identified.