Source : Webster's Revised Unabridged Dictionary (1913)

Mammal \Mam"mal\, n.; pl. {Mammals}. [L. mammalis belonging to
   the breast, fr. mamma the breast or pap: cf. F. mammal.]
   (Zo["o]l.)
   One of the Mammalia.

   {Age of mammals}. See under {Age}, n., 8.

Source : WordNet®

Age of Mammals
     n : approximately the last 63 million years [syn: {Cenozoic}, {Cenozoic
         era}]