Flatfishes (known to most as flounders) are an interesting group. Unlike other fish, they have two eyes on one side of their head, which allows them to lie flat on the sea bottom while still seeing with both eyes. Scientists have spent decades pondering how, during the process of evolution, this came about. A new discovery by Matt Friedman at Oxford University is providing paleontologists with clues to the flatfish’s seemingly unsolved history. Dr. Friedman found an unlabelled Eocene flatfish in a museum collection from Vienna. He identified it as Heteronectes chaneti, which means “different swimmer." Heteronectes has a flattened body like other flatfish, but its eyes are on either side of its head, suggesting that it lies somewhere along the evolutionary pathway between a common ancestor of all fish and the flounder. The fossil originally comes from Bolca, a town in northern Italy, a site where fossils are abundant. The Bolca quarry, known as “the fishbowl” for all of its marine fossils, is home to many 50-million-year-old fish and other coral reef fossils. The lack of oxygen at the site at the time of fossilization allowed exquisitely preserved fossils, like Heteronectes, to form. Further study of the mixed primitive and derived characters of Heteronectes promises to tell us more about the mysterious evolution of the flatfish.

Read more about the Bolca fossil site here.

The article about Heteronectes can be found at Sci-News.com.

Read the original study in the Journal of Vertebrate Paleontology.