45 2 



The Evolution of Fishes 



as deep, others arrow-shaped, and every intermediate form being 

 represented. An offshoot from this line is the bowfin (Amia 

 calva), among the Ganoids the closest living ally of the bony 



FIG. 261. An ancient Ganoid fish, Platysomus gibbosus Blainville. Family 

 Platysomidce. (After Woodward.) 



fishes, showing distinct affinities with the great group to which 

 the herring and salmon belong. Near relatives of the bowfin 

 flourished in the Mesozoic, among them some with a forked tail, 



FIG 262. A living Ganoid fish, the Short-nosed Gar, Lepisosteus platystomus 

 Rafinesque. Lake Erie. 



and some with a very long one. From Ganoids of this type 

 the vast majority of recent fishes may be descended. 



Another branch of Ganoids, divergent from both garfish and 

 bowfin and not recently from the same primitive stock, included 

 the sturgeons (Acipenser, Scaphirhynchus, Kessleria] and the 

 paddle-fishes (Polyodon and Psephurus} . All these are regarded 

 by Woodward as degenerate descendants of the earliest Ganoids, 

 Palaoniscidce, of Devonian and Carboniferous time. 



