Preheat oven to 250. Mix first 6 ingredients in large bowl to blend. Whisk buttermilk, pumpkin, eggs and melted butter in medium bowl until well blended. (Be sure to incorporate the butter before adding the buttermilk to avoid clumping.) Add to dry ingredients and whisk until smooth.
Spray large non-stick skillet with vegetable cooking spray and place over medium heat. Working in batches, drop batter by 1/4 cupfuls into skillet. Cook pancakes until bubbles form on top and bottoms are golden brown, about 2-1/2 minutes. Turn pancakes over. Cook until bottoms are golden brown, about 2 minutes. Transfer to baking sheet; place in oven to keep warm up to 20 minutes. Repeat with remaining batter, spraying with additional cooking spray as necessary for each batch.
Serve pancakes with hot maple syrup.