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Why is the fourth lower tooth often visible when a crocodile closes its mouth?

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Illustration of an estuarine or saltwater crocodile (Crocodylus porosus) with its mouth open, showing scaly skin and powerful limbs, alongside a scale bar for size reference. — crocodile Estuarine, or saltwater, crocodile (*Crocodylus porosus*), found in brackish waters from Sri Lanka, India, Bangladesh, and Myanmar east to the Solomon Islands and Vanuatu and south to Australia.

True crocodiles possess a narrow, V-shaped snout that differs significantly from the broad, U-shaped snout of alligators. Because of this jaw structure, the large fourth tooth on each side of a crocodile's lower jaw is positioned such that it projects outside the upper snout when the mouth is closed, making it clearly visible.1

In contrast, alligators have an "overbite" where all the lower teeth fit within the upper jaw, typically hiding them from view when the mouth is shut.1