The Collaborative International Dictionary of English v.0.48:

Vertebrata \Ver`te*bra"ta\, n. pl. [NL.] (Zool.)
   One of the grand divisions of the animal kingdom, comprising
   all animals that have a backbone composed of bony or
   cartilaginous vertebrae, together with Amphioxus in which the
   backbone is represented by a simple undivided notochord. The
   Vertebrata always have a dorsal, or neural, cavity above the
   notochord or backbone, and a ventral, or visceral, cavity
   below it. The subdivisions or classes of Vertebrata are
   Mammalia, Aves, Reptilia, Amphibia, Pisces, Marsipobranchia,
   and Leptocardia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Vertebrata
    n 1: fishes; amphibians; reptiles; birds; mammals [syn:
         Vertebrata, subphylum Vertebrata, Craniata,
         subphylum Craniata]