The Collaborative International Dictionary of English v.0.48:

Orthopoda \Or*thop"o*da\, prop. n. pl. [NL. See Ortho-, and
   -poda.] (Zool.)
   An extinct order of reptiles which stood erect on the hind
   legs, and resembled birds in the structure of the feet,
   pelvis, and other parts.
   [1913 Webster]