A fossil of a 50 million-year-old flatfish found in Italy shows an evolutionary intermediate stage between symmetrical-eyed fish and today's wacky-looking, asymmetrical-eyed halibut and other flatfish species. Scientists writing for the Journal of Vertebrate Paleontology say the fossil shows one eye beginning to move toward the top of the head.
The study provides the first detailed description of a primitive flatfish, revealing that the migrated eye had not yet crossed to the opposite side of the skull in early members of this group. Heteronectes, with its flattened form, shows the perfect intermediate stage between most fish with eyes on each side of the head and specialized flatfishes where both eyes are on the same side.
Read more at Sci-News.com: Fossil reveals secret of flatfishes
Note: Discover magazine points out this fossil discovery was originally reported on in more detail four years ago in the journal Nature.