forelimb: the front limb (or the homologous structure in other animals, such as a flipper or wing)
limb: one of the jointed appendages of an animal used for locomotion or grasping: arm; leg; wing; flipper
big-bang theory: (cosmology) the theory that the universe originated sometime between 10 billion and 20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature