Bryozoan fossil from the Ordovician of Ohio, USA.

This specimen is from the famous Cincinnatian Series of the tristate area of Ohio-Kentucky-Indiana. Rocks in the Cincinnatian were deposited in relatively shallow marine facies during the Late Ordovician. The Cincinnatian succession is mostly interbedded limestones and shales, all richly fossiliferous. Most of the limestones are event beds (= tempestites), deposited during ancient storms.

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 the bryozoan photo album) can be time-consuming, especially with large fragmented specimens.

Click on the photo to zoom in and look around - notice the numerous pits covering the bryozoan. 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, Bryozoa, Stenolaemata, Trepostomata

Stratigraphy: "Grant Lake Formation" (apparently from the Mount Auburn Member), Maysvillian Stage, middle Cincinnatian Series, Upper Ordovician