monotreme

from WordNet (r) 3.0 (2006)

monotreme
    n 1: the most primitive mammals comprising the only extant
         members of the subclass Prototheria [syn: {monotreme},
         {egg-laying mammal}]

from The Collaborative International Dictionary of English v.0.48

Monotreme \Mon"o*treme\, n. [Cf. F. monotr[`e]me.] (Zool.)
   One of the Monotremata.
   [1913 Webster]

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