loreal pit
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File:Groengele-groefkopadder-5.jpg. The loreal pit is visible between the eye and the nostril.]]
File:Diagram of the Crotaline Pit Organ.jpg
The loreal pit is the deep depression, or fossa, in the loreal area on either side of the head in pit vipers (crotaline snakes). The area is located behind the nostril and in front of the eye, but below the line that runs between the centers of each. It is the external opening to an extremely sensitive infrared detecting organ. The loreal pit is bordered by lacunal scales. The loreal pit also functions as part of a thermal regulating system, enabling pit vipers to maintain their body temperature.{{cite book |last=Campbell |first=J.A. |authorlink=Jonathan A. Campbell |author2=Lamar W.W. |authorlink2=William W. Lamar |title=The Venomous Reptiles of the Western Hemisphere |publisher=Comstock Publishing Associates |year=2004 |location=Ithaca and London |pages=870, 1500 plates |isbn=0-8014-4141-2 }}