• @[email protected]
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    12 years ago

    Yes, fish would be a morphology that includes gills, fins, streamlined body shape for swimming, etc. But there is no good phylogenetic definition because all the animals we call “fish” do not form a monophyletic group. The monophyletic group encompassing all fish would include also mammals, reptiles including birds, and amphibians because these all have fish ancestors

    • @[email protected]
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      12 years ago

      But there is no good phylogenetic definition because all the animals we call “fish”

      The challenge was to come up with a group “which includes both trout and sharks but not humans”. It seems like “gills” satisfies that pretty well.