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We classify 4-dimensional austere submanifolds in Euclidean space ruled by2-planes. The algebraic possibilities for second fundamental forms of anaustere 4-fold M were classified by Bryant, falling into three types which welabel A, B, and C. We show that if M is 2-ruled of Type A, then the ruling mapfrom M into the Grassmannian of 2-planes in R^n is holomorphic, and we give aconstruction for M starting with a holomorphic curve in an appropriate twistorspace. If M is 2-ruled of Type B, then M is either a generalized helicoid inR^6 or the product of two classical helicoids in R^3. If M is 2-ruled of TypeC, then M is either a one of the above, or a generalized helicoid in R^7. Wealso construct examples of 2-ruled austere hypersurfaces in R^5 with degenerateGauss map.

Ruled Austere Submanifolds of Dimension Four