The Collaborative International Dictionary of English v.0.48:

Acanthopterygian \Ac`an*thop`ter*yg"i*an\, a. (Zool.)
   Belonging to the order of fishes having spinose fins, as the
   perch. -- n. A spiny-finned fish.
   [1913 Webster]

WordNet (r) 3.0 (2006):

acanthopterygian
    n 1: a teleost fish with fins that are supported by sharp
         inflexible rays [syn: spiny-finned fish,
         acanthopterygian] [ant: malacopterygian, soft-finned
         fish]