Fish have been on the Earth for over 500 million years – long before even the dinosaurs roamed the planet. There are over 25,000 species – more than all the species of amphibians, reptiles, birds and mammals combined. Keep reading for more facts and information on fish. A fish is an animal which lives and breathes in water. All fish are vertebrates (have a backbone) and most breathe through gills and have fins and scales. Fish make up about half of all known vertebrate species. Fish have been on the earth for more than 500 million years. Fish were well established long before dinosaurs roamed the earth. The 25,000 known species of fish are divided into three main groups. There are three classes of fish: jawless, cartilaginous, and bony. All fish have a backbone. It is estimated that there may still be over 15,000 fish species that have not yet been identified. There are more species of fish than all the species of amphibians, reptiles, birds and mammals combined.The FamiLane Collection’s premium T-shirt should be a big part of any kids’ wardrobe. It wears rough and tough for kids who play the same way. Ideal for playing outside or sitting quietly doing homework, the premium T-shirt from the FamiLane Collection is as versatile and durable as it gets.