African freshwater fish Gnathonemus petersii in the order Mormyriformes. They grow to about 23 cm/9 in in length, have small eyes and fins and are mainly nocturnal. They generate an electric field which they use to detect obstacles. Elephant-trunk fish live in lakes in West and Central Africa.

Their brains are very large in proportion to their bodies: 3.1% of body mass compared with less than 1% for most fish and 2.3% for humans.