Evolution

A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. There are numerous examples of transitional forms in the fossil record, providing an abundance of evidence for change over time.

 

Pakicetus is described as an early ancestor to modern whales. Although pakicetids were land mammals, it is clear that they are related to whales and dolphins based on a number of specializations of the ear, relating to hearing. The nostril of Pakicetus, over time, moved to the top of the whale's head through evolution. This happened during thr process of this species moving from land to ocean. 

 

Transitional species/ fossils help to show the evolution of a species over time. They are the intermediate phases of the species from long ago to what they are now. They help to prove evolution.