Question

Why should one be careful with the term fish for a phylogenetic perspective?

Answer 1

From a phylogenic perspective, fishes are considered to be a primitive, more ancient organisms. A look at the phylogenic tree of modern mammals leads to a branching of tetrapods (from where the mammals evolved) from lobe-finned fish, which had earlier branched from Ray-finned and cartilageneous fishes. A few aquatic animals, who show a vaiety of characteristics and are/were a connecting link between the fishes and higher terrestrial organisms may also fall under the same category of fishes, by general usage of the term. The so-called gilled and finned aquatic organisms, denoted by the term fishes, in layman terms may also include some aquatic mammals. The term has a more specific meaning when it comes to evolution. Thus, the term Fish must be used carefully, when used in phyllogenic terms.