When I first read At the Mountains of Madness, I thought that the the description of the Elder Things (known in that story as "Old Ones") must have had almost perfect fivefold radial symmetry, like many modern echinoderms.
The first report of their appearance suggested to me that, along with their other ridges and appendages, the creatures probably had five wings, with one serrated wing folded up in each of the five furrows running along the body.
"10:15 P.M. Important discovery. Orrendorf and Watkins, working underground at 9:45 with light, found monstrous barrel-shaped fossil of wholly unknown nature; probably vegetable unless overgrown specimen of unknown marine radiata. Tissue evidently preserved by mineral salts. Tough as leather, but astonishing flexibility retained in places. Marks of broken-off parts at ends and around sides. Six feet end to end, 3.5 feet central diameter, tapering to 1 foot at each end. Like a barrel with five bulging ridges in place of staves. Lateral breakages, as of thinnish stalks, are at equator in middle of these ridges. In furrows between ridges are curious growths. Combs or wings that fold up and spread out like fans. All greatly damaged but one, which gives almost seven-foot wing spread. Arrangement reminds one of certain monsters of primal myth, especially fabled Elder Things in Necronomicon. These wings seem to be membraneous, stretched on framework of glandular tubing. Apparent minute orifices in frame tubing at wing tips. Ends of body shrivelled, giving no clue to interior or to what has been broken off there. Must dissect when we get back to camp. Can’t decide whether vegetable or animal. Many features obviously of almost incredible primitiveness. Have set all hands cutting stalactites and looking for further specimens. Additional scarred bones found, but these must wait. Having trouble with dogs. They can’t endure the new specimen, and would probably tear it to pieces if we didn’t keep it at a distance from them."
That was still the impression I had when I finished the story, that there were five wings.
However, almost all artistic depictions of the Elder Things seem to show them with just two visible wings. Here is a typical professional rendition of an Elder Thing, from Barlowe's Guide to Extraterrestrials. Wayne Barlowe has definitely given the alien only two wings; there is no room for the other others to be folded up between the creature's ridges.
Is there any basis, apart from the fact that flying creatures on Earth have two wings (or four for many insects), to think that the Elder Things had only two wings and not a fully symmetric five?