Phacops

Paleontologist Niles Eldredge used the Phacops trilobite in the 1970s as key evidence to formulate the theory of punctuated equilibrium alongside Stephen Jay Gould. They noted that these trilobites showed long periods of stability interrupted by sudden evolutionary changes.

Phacops is a genus of trilobite that lived predominantly during the Devonian period. Their fossilized remains are commonly found in ancient marine rocks, particularly in regions that were once shallow prehistoric seas.

Phacops is famous for possessing highly developed schizochroal compound eyes. Unlike the continuous lens systems of most other trilobites, this unique eye structure featured separated, large, biconvex lenses that provided acute depth perception.

Like many trilobites, Phacops could protect itself from predators by enrolling into a tight, defensive ball. This biological defense mechanism shielded their softer underbellies, leaving only their hard, armored exoskeletons exposed.