Researchers have evidence that an extinct species of monitor lizard had four eyes, a first among known jawed vertebrates. Today, only the jawless lampreys have four eyes.
Their evidence confirms that the pineal and parapineal glands weren't a pair of organs in the way that vertebrate eyes are. They also suggest that the third eye of lizards evolved independently of the third eye in other vertebrate groups.
Smith says that while there's "nothing mystical" about the pineal and parapineal organs, they do enable extraordinary abilities. For instance, they allow some lower vertebrates to sense the polarization of light and use that information to orient themselves geographically. Scientists still have a lot to learn about the evolution of these organs and their functions in living animals, the researchers say.
The new findings are a reminder of the hidden value within fossils left lying around in museums for more than a century."The fossils that we studied were collected in 1871, and they are quite scrappy -- really banged up," Smith says. "One would be forgiven for looking at them and thinking that they must be useless. Our work shows that even small, fragmentary fossils can be enormously useful."
Credit: Senckenberg Gesellschaft für Naturforschung / Andreas Lachmann / Digimorph.org
