Assuming that the fossils formed at the same time as the rocks they are found in, the oyster/stegosaurus fossils are the oldest fossils shown here.

a = executive branch; b = judicial branch

the circled areas are referred to   as sunspots.   the sunspots are cooler than the   surrounding area.

sunspots are temporary phenomena on the photosphere of the sun that appear visibly as dark spots compared to surrounding regions. they correspond to concentrations of magnetic field flux that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere.