A Headshot of a large predator from the Birrin world.
Upper eyestalks contain eyes and ears, lower contain eyes and sensory tentacles.
Most creatures related to the Birrin have 4 'lips' covering their jaws. However in this case the upper lip has evolved into a head shield which helps the creature push through dense forest. The blue membrane is used for display and can be retracted under a shield when not in use.
The animal hunts like a large heron, snatching smaller prey by shooting forward its long neck. It swallows most food whole, or by tearing it apart with its smaller inner jaws and toothed tongues.
And yes, those changes you have noticed over time are just part of the development progress. Now they all have two on top, two on bottom.