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Concept time!
The Devil's Marbles (or Karlu Karlu) are enormous granite boulders in Australia's Northern Territory.
The Northern Territory is home to what was once the world's largest Cattle Station: Victoria River Downs Station.
Combine the two? MARBULL. Huge boulder-bull hybrids that wander the deserts of PokeAus. (I'm not much of a drawfag, but here. They also draw inspiration from the devil aspect of the name)
Could easily be a Rock-type line
KARFU KARFU -> MARBULL
(calf + karlu karlu)->(marble+bull)