Marmosets are part of this scientific order that includes humans
[DOC] [TLE] Primate Factsheets: Pygmy marmoset (Callithrix pygmaea ... [PAR] Jun 30, 2005 ... Pygmy marmosets are the smallest monkeys in the world, weighing a mere 119 g 
... from the flat nails (called ungulae) seen in other primates, including humans, ... 
are isolated by geographic barriers which include several large rivers.