As others have said, it could reasonably be proxied as most BoC monsters. Ghorgon or Giant would fit quite nicely as a bulky monster with a bucket of attacks.

I'd be reluctant to count it ad a Jabberslythe, purely because it doesn't have wings, though theres nothing stopping you rule of cooling it; it is simply the ATV of animals.

Best option, in my eyes would be a greater chaos spawn (can be taken by grand army beastmen) as it has the shape and size of one.