This dead monstrosity is the heaviest bony fish in the world

Lungfish and bichirs do. Apparently lungs are ancestral in bony fish, even though the great majority have replaced them with a swim bladder.


That is what is interesting.

Modern scientific classification is usually based on genetics and common ancestors. From that point of view, there isn’t really any satisfactory definition of a fish at all. Lungfish and coelacanths have a more recent common ancestor with humans, whales, and elephants than with the sunfish, while all bony fish are more closely related to us mammals than the cartilaginous fish like sharks and rays.

So while tetrapods which includes amphibians, reptiles, and mammals is traditional excluded from “fish” and “bony fish”, that is mostly a convenient grouping based on physical characteristics and habitat rather than phylogenetic similarity. To be clear, there is nothing wrong with classifying things this way: there are plenty of useful ways to classify things other than following a particular scientific convention.

It’s not purely an issue of nomenclature, it helps us understand biology and evolution. As chenille mentioned, a handful of fish do have lungs, and the common ancestor of all bony fish had lungs, but almost all of the ray finned fish lost them while lungfish retained them and tetrapods evolved to live on land.


Interesting. I guess the early taxonomists didn’t realize how many edge cases there would be :slight_smile:

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