Orbits of s-representations with degenerate Gauss mappings
  In this paper we study tangentially degeneracy of the orbits of s-representations in the sphere. We show that an orbit of an s-representation is tangentially degenerate if and only if it is through a long root, or a short root of restricted root system of type G_2. Moreover these orbits provide many new examples of tangentially degenerate submanifolds which satisfy the Ferus equality. 
Osamu Ikawa, Takashi Sakai and Hiroyuki Tasaki