Congenital digital aplasia in a free-ranging group of silvery marmosets, Mico argentatus.

Congenital aplasia of the hallux (big toe) was observed in seven adult and infant members of a free-ranging group of silvery marmosets (Mico argentatus) in the Alter do Chão savannah of central Amazonia. Apparently heritable, the condition was more common in males (80%) than females (50%) but was found in no other members of the population. Animals with the condition presented normal behaviour.