Parietal eye
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A parietal eye is a part of the epithalamus in some vertebrates. The eye is at the top of the head, is photoreceptive, and is associated with the pineal gland, which regulates circadian rhythmicity an
The parietal eye (very small grey oval between the regular eyes) of a juvenile bullfrog (Lithobates catesbeianus)
Adult green anole (Anolis carolinensis) clearly showing the parietal eye (small grey/clear oval) at the top of its head
Parietal eye of the Merrem's Madagascar swift (Oplurus cyclurus) is surrounded by a black-and-white spot on the skin, giving it the "three-eyed" appearance.
Parietal eye of a regal horned lizard (Phrynosoma solare)
Lamprey
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Lampreys are a group of jawless fish composing the order Petromyzontiformes, sole order in the class Petromyzontida. The adult lamprey is characterized by a toothed, funnel-like, sucking mouth. The co
Parietal eye
…become popularly known as the "third eye". The parietal eye is found in the tuatara, most lizards, frogs, salamanders, certain bony fish, sharks, and lampreys. It is absent in mammals but was present in other extinct members of Synapsida including Therapsida. The pineal foramen became completely closed over…
Jõesilmud 2
Mouth of a sea lamprey, Petromyzon marinus
Median section of lamprey demonstrating internal anatomy
The cartilaginous skeleton of a lamprey washed up on a beach in North Carolina.