Clavam are a type of creature which use their clubs to beat their prey until it is immobilized. The Clavam then use their mouths to inject a liquid which decomposes the prey into a mushy goo which they can then suck up for nutrients. The large club on their tail means they cannot be very agile but still pose a threat. I'm not very good with sprites but here is a little example of what it would look like as one. It would fight similar to an Ankylosaurus I'll try to add more (or make a sample sprite) when I can.
Let's see... Could it possibly use the stinger/needle-like mouth to attack BEFORE beating its prey into submission? Like maybe a poison attack? And does the club-tail touch the ground? Because if not I don't see how it balances and if that were how it moved, having to hop that thing along, it would be pretty awesome; it would add more originality and be funny. ALSO, building on the latter idea, what if it attacked by like, flipping its whole body except its legs to bring the club over its head and down (as opposed to spinning horizontally)?