The average sea pig has a fat, oval body, with a length ranging from 5 to 10 cm (2 to 4 inches). The mouth is surrounded by ten feeding tentacles and they have five to seven pairs of feet, that are used exclusively for walking on the sea bottom.
They have three pairs of papillae on the upper surface of the body. The two are long and whip-like, but the third pair is short and inconspicuous.
Currently, there are 5 described scotoplanes species:
- Scotoplanes clarki
- Scotoplanes globosa
- Scotoplanes hanseni
- Scotoplanes kurilensis
- Scotoplanes theeli