The aquatic reptile fossil pictured is a Mesosaurus brasiliensis found in the Irati Formation of Brazil. It dates back 280 million years ago (Lower Permian Period). The museum display lists this fossil as one that shows the transition of reptiles to a freshwater environment. It also shows that the continents Africa and South America were connected since this creature's fossils are only found in those two places.
The reptile was thought to its narrow teeth rowed mouth was used to catch fish and other small aquatic creatures. It swam though the water using is long tail and paddle shaped limbs.
The fossil was loaned by Robert H. Osher family to the museum for exhibit.
Fossil on display at Cincinnati Museum of Natural History & Science as of August 2013.