monotypic

from WordNet (r) 3.0 (2006)

monotypic
    adj 1: consisting of only one type

from The Collaborative International Dictionary of English v.0.48

Monotype \Mon"o*type\, Monotypic \Mon`o*typ"ic\, a. [Mono- +
   -type: cf. F. monotype.] (Biol.)
   Having but one type; containing but one representative; as, a
   monotypic genus, which contains but one species.
   [1913 Webster]