It's not a scarab at all, instead it's a bird that has developed a minor amount of armour for its back and neck/head. This armour is not to protect it from blows, needing to be light and is probably a collection of fused feathers, so it's actually used to protect itself from sandstorms.
When it detects a sandstorm it lands and settles into the sand, digging its feet into the sand as an achor and then tucking its wings and tail and head under its 'shell' to avoid damage from being sand-blasted. Once the sandstorm is over it digs itself out of whatever collection of sand it has no doubt found itself buried under and continues about its merry way.
As for the beetle-like forelegs... it could be a pronounced but in the end functionally useless head/beak feature/protrusion(s) like many birds have that is used during mating as is being perpetuated via sexual selection. I'm imagining a more forward-facing and stiffer version of what the king of saxony bird of paradise has got going on.