The Collaborative International Dictionary of English v.0.48:
Crossopterygian \Cros*sop`ter*yg"i*an\ (kr?s-s?p`t?r-?j?-an), a. (Zool.) Of or pertaining to the Crossopterygii. -- n. One of the Crossopterygii. [1913 Webster]WordNet (r) 3.0 (2006):
crossopterygian n 1: any fish of the order Crossopterygii; most known only in fossil form [syn: crossopterygian, lobefin, lobe- finned fish]