tetrapod

from WordNet (r) 3.0 (2006)

tetrapod
    n 1: a vertebrate animal having four feet or legs or leglike
         appendages

from The Collaborative International Dictionary of English v.0.48

Tetrapod \Tet"ra*pod\, n. [Gr. ? fourfooted; te`tra- (see
   {Tetra-}) + ?, ?, foot.] (Zool.)
   An insect characterized by having but four perfect legs, as
   certain of the butterflies.
   [1913 Webster]