From western Argentina, Tephrocactus articulatus var. diadematus is a nearly spineless form of the species. At least none of the ones in my collection ever formed spines except for some small glochids on the new growth. These usually fall off as it ages. Segments generally grow longer and narrower than var. papyracanthus, reportedly up to a foot tall. Mine are generally a bit shorter than that. The flowers are very similar to var. papyracanthus though I've never had any flower.
     I got a cutting of this about twelve years ago and have grown and given away many of them. The one above is unusual because, at least in my experience, the segments usually grow one or two new segments each year from the stem tips. This is the first one I've ever seen with several new segments growing from the sides of the stem. I think it is going to be an interesting specimen if that continues. The picture below is of a nice patch in my garden after a rain. The low light because of the cloud cover gave it a nice blue hue.
     I've never had a flower but Xenomorf, a fellow member of the Davesgarden.com gardening forums has consented to letting me use his pictures. Thanks Xeno :-) Also check out the gallery of Xenomorphs pictures in the Galleries/Friends section.

A nice one in my yard

Flower by Xenomorph

Flower by Xenomorph