An example is the genus Darlingtonia, the only member species of which is Darlingtonia californica.
Another example is the species homo sapiens sapiens (people), which, as of the end of the twentieth century, is considered to be indivisible into seperate sub-species or races.
See race for a more detailed definition of monotypic in the context of a species, and its relevance regarding the species homo sapiens sapiens.