On this Fish batter no beer the language links are at the top of the page across from the article title. Fish come in many shapes and sizes. They are camouflaged as floating seaweed.

Dunkleosteus, a giant armoured arthrodire of the later Devonian. Up to 6 metres long, it lived in the Inland seas of North America. Fish used to be a class of vertebrates. There are many different kinds of fish. They live in fresh water in lakes and rivers, and in salt water in the oceans. Some fish are less than one centimeter long. The English word “fish” does not fit neatly into cladistics, which is the scientific way to put living things into groups.

So scientists call it a paraphyletic word. This means that the animals called “fish” in English do not fit into just one phylum. Some fish are more closely related to land animals than they are to other fish. Fish” is not a formal taxonomic grouping in systematic biology. But the use of the term “fish” is so convenient that we go on using it. Fish are the oldest vertebrate group. The term includes a huge range of types, from the Middle Ordovician, about 490 million years ago, to the present day.