I can only find one source that discusses their purpose, and it seems specious: https://www.livescience.com/12864-google-earth-saudi-archaeology-tombs.html
Is it really quite likely that nomadic shepherds constructed these thousands of large structures across such a large swathe? Would the “tails” of some of these structures really need to be so wide if their purpose was only for corralling animals? And on that note, why would they need such a large circular “base” if that was their primary function? Why would many of these structures extend into town-like areas that were seemingly inhabited? Why would some of these be located at the tops of mountains without any tails that extend into the distance? Why do some have “breaks: in the wall, completely defeating the purpose of corralling animals altogether? Why are the interiors of some of these so elaborate? Why would some not appear well-constructed for the purposes of corralling whatsoever?
It seems to me like these are the result of a coordinated effort by a large civilization. What was the civilization most likely responsible? I haven’t been able to find anything that fits the geography and the likely timeline, but there is a reference to what is quite possibly a “lost region(?) of pillars” called Iram. I’m really reaching now, but could these structures be considered “pillars”, just flat rather than vertical?
Would appreciate any information possible about these.
As noted in the little article you cited, the modern Saudi government does not want serious archaeological investigation, because it will invariably contradict their religious beliefs. Nonetheless, we are not completely ignorant on this topic. If you were hoping for aliens, I'm sorry to disappoint you.
The structures in your linked images are not a unified group. They are not even all from the same time period or region. The ancient Arabian landscape was dotted with various constructions, including tombs, cairns (piles of rocks basically), walls, megaliths, et cetera. Most are from the late Neolithic and were constructed/carved/piled by nomadic hunter-gatherers as they crisscrossed western Arabia. Like all megaliths of this time period throughout Europe, Africa, and the Near East, they are somewhat enigmatic. We don't know precisely why they built them, or why some groups built them while others did not.
The heyday of megalith construction in western Arabia is the end of the "Holocene Wet Phase," about the middle of the 4th millennium BCE. At this time there is a mixture of sedentary agricultural/herding communities existing alongside nomadic hunter-gatherers. It is widely assumed that the latter group are responsible for the majority of the constructed features, constructed sporadically over the next two millennia, down to the end middle of the 2nd millennium BCE. Although there has never (to my knowledge) been any sort of real investigation, photographs, drawings, and notes from the pre-war era have been meticulously studied. Arabia is also not the only place such rock art installations have been found (Yemen and Jordan also have identical structures, e.g.).
You are asking in particular about the "kites," the circular cairns with what you call "tails" (often now called pendants). They were termed "kites" by British RAF pilots during WW2, who continually noticed them dotting the landscape. Examples in Saudi Arabia are not well known, but examples in Syria and Jordan have been thoroughly investigated. They are generally understood to be "kill traps," or in other words, constructed features that serve to corral animals which are being chased, so they can be run down and killed. Large assemblies of herd animal bones have been found in association with them. The "kites" of the north area are thought by some to differ from the "pendants" generally clustered further south, and their compositions sometimes differ (as you note). It is not clear exactly what the implications are.
Separate from these are the stone pile mounds for burial, which are very common (there are thousands). Bronze weapons, pottery, etc, like "warrior graves" in Europe. These also sometimes have linear "tails" or "pendants" in association with them. Some kind of megalithic symbolic tendency seems obvious to me, much like the henges of western Europe about the same time. Astronomical notation of some sort, perhaps. Further investigation is needed.
For the time period in Arabia, see Magee, The Archaeology of Prehistoric Arabia. Adaptation and Social Formation from the Neolithic to the Iron Age (Cambridge 2014).
See also Newton and Zarins, "Aspects of Bronze Age art of southern Arabia: The pictorial landscape and its relation to economic and socio‐political status" (*Arabian Archaeology and Epigraphy 11(2)[2003]:154-179).
