File:Bryozoans in fossiliferous limestone 4.jpg

English: Fossiliferous limestone is a clastic-textured, biogenic sedimentary rock. It's usually composed of calcite (CaCO3 - calcium carbonate), but some geologically young examples consist of aragonite (also CaCO3). A typical fossiliferous limestone is grayish-colored with whole fossils, fragmented fossils, and fine-grained matrix - often mud. Most were deposited in warm, shallow, tropical ocean environments.

This limestone is dominated by bryozoan fossils. Bryozoans are colonial lophophorates, most of which make a calcareous skeleton. Many bryozoan skeletons have complex shapes that usually cannot be fully appreciated from the fossil record. Bryozoans are abundant fossils, especially in Paleozoic and Mesozoic limestones, but their skeletons usually get busted up during the storm events resulting in their final burial. Colony reconstructions (see elsewhere in this photo album) can be time-consuming, especially with large fragmented specimens.

Numerous tiny pits cover bryozoan skeletons. The pits are zooecia - each zooecium housed an individual bryozoan animal, called a zooid. Zooids have a ring of tentacles that filter the water for tiny particles of food. All bryozoans are sessile, benthic filter-feeders.

Classification: Animalia, Lophophorata, Bryozoa

Stratigraphy: unrecorded, but very likely from the Cincinnatian Series, Upper Ordovician

Locality: unrecorded, but very likely from the Cincinnatian outcrop belt of southwestern Ohio-southeastern Indiana-northern Kentucky, USA