Possible Clues:

• German-born painter, Max, co-founder of dadaism, d. 1976
• Artist who contributes to postmodern style
• Max --, German painter
• Ultimately one superior in his art
• Surrealist called familiarly 'the most'
• He painted birds head to toe
• Positivist philosopher Mach
• Celebrated surrealist Max
• Surrealist who painted 'Forest and Dove'
• With 61-Across, physicist who studied supersonics