Trilobites

Research in the park by Charles Walcott on trilobites in the late 1800s provided the foundation for his theory of the “Cambrian Explosion,” a term he used to describe the relatively sudden appearance of complex multi-cellular life possessing “hard parts” such as phosphatic or calcitic exoskeletons.

Stromatolites are the limestone structures formed by photosynthesizing bacteria called cyanobacteria. They created layers of alternating slimy bacteria and sediment in very shallow water, dominating shallow seas until predators, such as trilobites, came into the picture.

Trilobites fossils are arthropods, or joint-footed animals, with a segmented body of hinged plates and shields. They could curl up into a ball for protection, sometimes fossilizing as a "rolled" trilobite.

Like arthropods today, trilobites molted as they grew, shedding their old exoskeleton. These molts could fossilize, so one animal could leave several different sized fossils behind.

Even though trilobites were relatively primitive animals, they had amazingly complex eyes. Many species had faceted eyes like an insect, using up to 15,000 lenses in one eye.

It is during this period that Earth suffered one of the largest mass extinctions in history, losing 50 percent of its animal families, 95 percent of all marine species, many species of trees, and the trilobites.