There are specimens known of Phacops rana with many irregular black spots. Because similar spots in a specimen of Greenops boothi from the same site are arranged in rows, it may be assumed that they are original and not caused by the fossilisation process. The spots are irregular and have spurs branching outwardly, similar to the melanophores in many extant animals. In one specimen, the black spots are much larger than in another one. It is quite conceivable that changing the size of the melanophores enabled Phacops rana to camouflage itself in different environments.
