REP: The crestheads

Crestheads are omnivorous tentaculopods found mostly in slow-flowing rivers and lakes. Their first two pairs of smelling knobs evolved into dexterous tentacles they use for manipulating food. Their heads reach over their short, powerful jaws and sport distinctive head crests, which serve for communication and display. Crestheads live in small groups, searching the river groung for food.

Inverse fisher: A rather unusual cresthead that lives solitary and adapted to a predatory livestyle. It swims upside-down at the surface and lures pneumonopteres with its second pair of tentacles, then catches them with its elongated lower jaws.
Clappercrab: A species which lives in murky waters and uses its tentacles additionally for orientation. Its crest is underdeveloped and it communicates by clapping its jaws instead.
Water amphisbena: Usual livestyle, but unusual form, which serves for distracting predators. To make their front and rear even more unclear they move often backwards.