Source : Webster's Revised Unabridged Dictionary (1913)

Crossopterygian \Cros*sop`ter*yg"i*an\ (kr?s-s?p`t?r-?j?-a]/>n),
   a. (Zo["o]l.)
   Of or pertaining to the Crossopterygii. -- n. One of the
   Crossopterygii.

Source : WordNet®

crossopterygian
     n : any fish of the order Crossopterygii; most known only in
         fossil form [syn: {lobefin}, {lobe-finned fish}]