File:Rugose coral & spiriferid brachiopod & trilobite tail (Silica Formation, Middle Devonian; Lafarge Paulding Quarry, near Paulding, Ohio, USA) 1 (48911141406).jpg

Fossil coral & brachiopod & trilobite in the Devonian of Ohio, USA.

At top is a coral fossil. Corals are essentially sea anemones (polyps) that make a skeleton, which is usually mineralized. Most corals are colonial, but some are solitary. This is a solitary rugose coral, also known as a "horn coral", in reference to the tapered solid skeleton (best seen on weathered-out specimens).

At left is a spiriferid brachiopod fossil. Brachiopods are sessile, benthic, filter-feeding, marine invertebrates. They first appear in Cambrian rocks and were abundant in Earth's oceans throughout the Paleozoic. They were also common in Mesozoic oceans, but are scarce in modern oceanic biotas. Brachiopods have two shells, called valves, that are usually calcareous (made of calcite - CaCO3 - calcium carbonate). Each shell of a brachiopod is bilaterally symmetrical, unlike each shell of a bivalve (clam).

At right is a trilobite tail, technically called a pygidium. It is from a Phacops trilobite (also referred to by the subjective junior synonym Eldredgeops). Trilobites are extinct marine arthropods that range in age from the Cambrian to the Permian. They had a calcitic exoskeleton with soft parts underneath (gills, legs, guts, etc.). From front to back, the trilobite body consists of a head (cephalon), a body of many segments (thorax), and a tail (pygidium). The exoskeleton is also divided into three parts longitudinally, with an axial lobe running down the middle, and two pleural lobes (side lobes).

Stratigraphy: Silica Formation, Middle Devonian