Sur-Snake

The Sur-Snake is a non-sapient aquatic beast native to planet Argo.

Biology
With both gills and lungs, this venomous predator can operate as well on land as underwater, but prefers the latter. They are elongated creatures with four pairs of long, almost tentacle-like fins. Their skeletal structure is described as being similar to that of Denebian Whales.

Strangely, the Sur-Snake's venom has the property of reversing the mutation developed by the Aquans which causes humanoids to grow gills and webbed feet. This indicates that the venom operates on a genetic level on the Sur-Snake's victims, which is highly unusual. It is possible that the venom acts this way to cause the snake's victims to lose gills and drown, allowing them to be easily consumed by the predator.

Appearances

 * Star Trek: The Animated Series, s01e13, "The Ambergris Element" (1973)