Dr. Thakkar was studying a fossil from a dig in a desert when he noticed that the organism had evidence of fins. What would this most likely tell Dr. Thakkar?

This would mostly tell Dr. Thakkar that this is a sea creature that died when the sea levels where higher

This prehistoric fish fossil brings an evolutionary light. Dr. Thakkar most likely was digging in a desert terrone that once housed a sea. The creature has died, millions of years have passed, the sea has dried up, millions of years have passed, the desert has grown, and the fossil of an aquatic creature has been preserved in an arid environment.