For more, see my earlier post. But here's a piece from Al Jazeera about one of them, Soqotri, (which the article spells Socotri), spoken on Yemen's island of Soqotra. Because of itsinsular loction, it is the most distinctive of the Modern South Arabian language, with little mutual intelligibility with the others.
The article deals with the work of Russian linguists who began to study Soqotri during the era of Soviet influence in South Yemen. It adds some color to my earlier post, from which I take a map and a video of Soqotri poetry: