Page "Hippocampus" Paragraph 59

Thus, the role of the hippocampal region in navigation appears to begin far back in vertebrate evolution, predating splits that occurred hundreds of millions of years ago.

It is not yet known whether the medial pallium plays a similar role in even more primitive vertebrates, such as sharks and rays, or even lampreys and hagfish.

Some types of insects, and molluscs such as the octopus, also have strong spatial learning and navigation abilities, but these appear to work differently from the mammalian spatial system, so there is as yet no good reason to think that they have a common evolutionary origin ; nor is there sufficient similarity in brain structure to enable anything resembling a " hippocampus " to be identified in these species.

Some have proposed, though, that the insect's mushroom bodies may have a function similar to that of the hippocampus.