CREATE TABLE table_name_41 (longitude VARCHAR(255), name VARCHAR(255), year_named VARCHAR(255), diameter__km_ VARCHAR(255))
What's the longitude named zipaltonal fluctus in 1997 with a diameter smaller than 490?
    
SQL: SELECT longitude FROM table_name_41 WHERE year_named = 1997 AND diameter__km_ < 490 AND name = "zipaltonal fluctus"