Penguins

 NY Times: How Penguins Beat the Heat and Went South - Scientists reconstructed some of the evolutionary steps that led penguins to quit tropical climates for the Antarctic life over millions of years. By Jack Tamisiea

Species like the emperor penguin have overlapping layers of insulating plumage, tightly packed veins to recycle body heat and just enough paunch to weather wind chills that approach minus 80 degrees Fahrenheit.