[hasanas]

I am assuming the article is contrasting the long periods of nomadic lifestyle that ruled over Arabia with the more stationary society suggested by the existence of those mustatils.

As for the heads of the cattle, I can easily imagine the mustatils to be some sort of combination farm-market where you would kill the cattle, burry the head, and give the rest to the consumer who would take it far away to their dwelling or on their journey if they happen to be nomadic; leading to random distribution of the rest of the carcass pieces.