In some lizards and the tuatara, the paired lateral eyes are augmented by another sense organ.
| Question | Answer | Article | |
| What is this organ? | The parietal eye. |
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| What is the function of this structure? | The parietal eye detects shadows and, thus, perceives the potential threat of predators. It also serves as a dosimeter of light and, as such, helps regulate the diurnal basking activities of reptiles that possess these accessory light-sensitive organs. |
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