This is an example of a homologous structure. Homologous structures are anatomical features which have the same organisation but different function (they do different jobs but are “put together” in the exact same way,)
The fact that the bones are the same tells us these organisms have a common ancestor. They have the same structure Because they inherited it from a common ancestor (it has been passed down) who had this structure. This supports evolutions because it proves that organisms inherit features from parents.
But these structures they have variations - like length and shape. This is because they have adapted this structure of suit different environments.
This supports evolution which states that organisms survive dues to the presence of advantageous adaptations.
These homologous structures are an evidence of adaptation.