Origin: 1825–35; < NL monotrematus lit., single-holed, equiv. to mono-mono-+ -trematus -holed, adj. use of Gk trêma, s. trēmat- hole, perforation; see -ous
mon·o·treme (mŏn'ə-trēm') n. A member of the Monotremata, an order of primitive egg-laying mammals restricted to Australia and New Guinea and consisting of only the platypus and the echidna.
[From New Latin Monotrēmata, order name : mono- + Greek trēma, trēmat-, perforation; see terə-1 in Indo-European roots.] mon'o·trem'a·tous (-trěm'ə-təs) adj.