Ammonoids

Ammonoids are basically big shell-snails living in the dark caves of Mars. It is not uncommon for them to travel in groups. Although rather big, they are rather clumsy in combat and easily vanquished. The main problem is, that they also attack with a rather nasty acid, which can really hurt and damage the equipment.

They can be found in the dark, martian caves.

Lore
''This primitive, snail-like creature dwells exclusively in the dank. dark Martian underworld. Its spiky, thorned shell provides ample protection against attack. Its tentacles allow it to grasp prey, but the real danger posed by the ammonoids is the burning acid secreted from suckers on the lower tentacle surface.''

- from "Mysteries of the Red Planet", Martian Dreams