Some animals lack limbs with digits, and these are known as fish. Other examples of fish are lampreys, hagfish, and cartilaginous and bony fish. Among these extinct groups, tiger sharks and crocodiles are also aquatic. In this article, we will briefly discuss some of these extinct species and groups, as well as a few others. This will give us a better understanding of the nature of fish.
Despite these differences in size, fishes generally have many similarities, which is why they are classified as “fish.” Some types of fish are more related to one another than others, but despite the similarity of their appearance, a fish will have a different skeleton than a ray. Some species of fish may have two skeletons, but they are still classified as “fish.” The difference in skeletal structure between sharks and fishes is important to understanding the biology of these creatures.
Many divers know that groupers and gobies are fish, but many don’t know that sharks, rays, eels, and sea horses are all fish. This is because the former two are not related to each other, while the latter are 100 percent fish. However, it is impossible to determine which animal is related to which. That is because all of these species have the same skeletal structure. And this means that the differences between them are minimal.