Right, I was thinking of the marine fishes not chewing much, but freshwater fishes chewing due to having more amphibious ancestors at some time, and so having been selected via survival in drier climates, where suction feeding doesn't work outside of water. Their chewing muscles and tongue are probably less well developed than terrestrial chewing animals, but much better than ocean fish.
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Others 'walk' on strong fin rays. Plecos and Corydoras do not leave the water often, but they can stand on their fins, and I have seen small plecos 'walking' underwater on a sandy substrate, using their strong and spiny fins with a movement like a salamander.
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Do these fin walkers move their fins out laterally to the sides and paddle (like oars) in very shallow water? Or is the walking limited to nonshallows?
I think all these freshwater must have had lobe fins which since disappeared, or developed a eel-like crawl, or directional flipping, in the past, and this selected for better air breathing as a result.
I guess polarized vision might also be selected for under those conditions.
