Evolution brings new traits and features to living things. This is part of a species adapting to a new environment. As a species goes to a new place, slowly it adapts over time to acquire a new trait or feature. One example of this is the evolution of the tail, whose evidence is found in the fish fossil.
An ancient fish has shown that early in its life it had two tail outgrowths. One is a fleshy tail while the other is a flexible fin. As the fish grows, one of those features gradually disappeared. Modern day ray-finned fishes have been seen as well to have this early trait.
The fossils of the early fish have never been studied before. These fossils represent the early stages of Aetheretmon valentiacum, which is related to modern day fishes. Some of the fossils are as small as three centimeters long.
The adult Aetheretmon fish would eventually have a tail that is longer at the top than at the bottom. This trait is still found in some fishes today. Sturgeon and paddlefish possess this trait, and have been referred as modern fossils since they still retain many ancient fish characteristics. Most modern fishes, on the other hand, have a more symmetrical tail. This two-part structure of the tail has been around for some time in both living and extinct fishes.
Lauren Sallan, assistant professor in the Department of Earth and Environmental Science at the University of Pennsylvania said that modern and ancient fishes have a similar starting point. At some point the tail structure began to be adjusted on modern fishes, according to Penn News. This two-tail structure would be adjusted on modern fishes later on.
The two-tail structure would also be found in modern land-based animals such as the tetrapods, as Science Daily reports. The outgrowth on Aetheretmon will ultimately be the tail in many animals later. Sallan said that the two structures might have been controlled by the genes, so that later on this trait would find different forms of adaptation in various creatures.
Evolution has shown that adaptation would lead to different structures in animals. An example of this is the evolution of the tail, whose evidence is found in the early fish fossil. Adaptation can be found also in human evolution, as one of the earliest hominids has been a tree climber.