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Paleozoic Partner Highlight

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Global paleogeographic reconstruction of the Late Ordovician 450 million years ago and a reconstruction of life in the Cincinnatian ocean. The position of Cincinnati on the paleocontinent Laurentia is highlighted (red star). Paleogeographic map by Ron Blakey (Colorado Plateau Geosystems). Ocean life reconstruction by John Agnew (2007).

Cincinnati Museum Center (Cincinnati, Ohio)

Under the Sea in the Southern Hemisphere

The layered strata that can be seen along the numerous road cuts and in streambeds in the vicinity of Cincinnati are among the most fossil rich regions in North America. As a testament to their scientific significance, these rocks are known as the North American Upper Ordovician Type Standard. To study Earth's history 450 million years ago, the best place in North America is the famous Cincinnatian Series.

These outcrops of strata represent muds and limestones that were deposited over the course of millions of years on an ancient shallow tropical ocean bottom. This time in North American history looks very different from our modern perspective. North America as we know it didn't exist, but its predecessor, Laurentia, was a southern hemisphere continent mostly covered by a warm, shallow ocean. At this time, the majority of life on Earth was in the oceans—representing most major phyla of organisms known today. Brachiopods and bryozoans comprise the greatest proportion of the biomass, but crinoids, trilobites, bivalves, corals, and gastropods are abundant and diverse. Annelids provide a rich trace fossil record, signaling the diversity of soft-bodied life within the oxygenated substrate at this time. Even though vertebrates, in the form of agnathan fish, had evolved by this time, this was definitely an invertebrate dominated world with every ecological role—from detrital feeder to predator—occupied by invertebrates.

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The Ordovician trilobite Isotelus maximus is the state fossil of Ohio (link to PDF).

There are a variety of reasons why this region continues to be a hotbed for paleontology. The Cincinnatian Series is at the end of a pivotal evolutionary event for life on Earth. During the onset of the Ordovician period, life experienced the greatest evolutionary biodiversification event in the history of the Earth. As a result, the number of species in the oceans exploded culminating in the astounding diversity of fossils found in this region. These fossils are exquisitely preserved. Rapid burial by submarine mudflows at the bottom of the ocean provided protection from wave energy and scavengers that might otherwise destroy animal remains. The numerical abundance of fossils is also amazing. Try to pick up a rock from this region without a fossil in it—it's hard to do!

Our incredible rocks and fossils have attracted much worldwide attention for well over 100 years. A long legacy of scientific research in American paleontology and stratigraphy was accomplished here. Cincinnati paleontology grew out of research publications from "gentlemen naturalists" that were passionate collectors and amateur scholars in the latter part of the 19th and early 20th centuries. This legacy of scientific research is still ongoing today, with the University of Cincinnati Department of Geology cited as one of the foremost paleontological programs in the country.

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The official City of Cincinnati fossil, Isorophus cincinnatiensis, was decided by public vote at Cincinnati Museum Center and declared by the mayor of Cincinnati in 2002. Isorophus is a edrioasteroid ("seated star"), an extinct group of echinoderms.

Cincinnatian fossils are displayed in museums all over the world. Scientists regularly visit Cincinnati Museum Center's research collections—one of the largest Upper Ordovician collections in the world. Whether through the legacy of major contributions to science by historical and current paleontologists, or the abundance, diversity, and preservation of organisms found in this regions outcropping strata, Cincinnati has a unique resource that continues to make significant contributions to understanding the Earth's past.

Please visit Cincinnati Museum Center's website for more information. Detailed information on the Invertebrate Paleontology collections can be found at

The Mission of Cincinnati Museum Center is to inspire all people to understand and appreciate natural history, science, and regional history; and to support the development of children. We collect and preserve; we advance and share knowledge. We stimulate curiosity and promote enjoyment of learning.

Article and photographs provided by Dr. Brenda Hunda (Cincinnati Muesum Center paleontologist).

2013 Paleozoic Partner feature articles:

| January: Fossils of the 2013 National Fossil Day Artwork | February: Paleontological Research Institution, Museum of the Earth | March: Falls of the Ohio State Park | April: Field Museum of Natural History, Mazon Creek Collection | May: Prehistoric Trackways National Monument | June: Cincinnati Museum Center | July: Glacier Bay National Park & Preserve | August: University of Michican Museum of Paleontology, Silica Formation Fossils | September: Yale Peabody Museum of Natural History, Beecher's Trilobite Bed | October: Guadalupe Mountains National Park | November: Utah Geological Survey, Millard County Cambrian Fossils | December: Denver Museum of Nature and Science, High-Altitude Mass Extinction |

Last updated: May 31, 2013