Now known for its sports teams, Harleys, and beer, early Milwaukee County, Wisconsin was one of the nation’s leading producers of natural cement, and the fossils from its cement mines revealed one of the country’s most diverse assemblages of animals and plants of their age (Middle Devonian, ~385 million years ago). With the depletion of the cement rock, so went the ‘era of discovery’ of those fossils, but the few remaining exposures have become an important Geoheritage site, and museum collections still house many thousands of fossils that can be prepared and used for research, display, and educational purposes.
From 1876 to 1911 rock obtained from the Middle Devonian (~385 million years ago) Milwaukee Formation produced not only much of the country’s natural cement, but many thousands of fossils from a wide variety of environmental settings, representing around 250 species, 100 families, 16 phyla, and four kingdoms.
This remarkably large number of taxa, some known from only a few specimens, is attributed to unusually intense collecting by amateur and professional geologists, and to a greater extent, numerous quarry workers who were paid by wealthy amateurs for their best fossils.
Had other Middle Devonian occurrences been collected this intensely, some may have yielded similar results.
Although the fossils were preserved in marine sediments, some plants, trees and giant fungi were washed into the sea after living in terrestrial environments, buried in the sediment, and fossilized along with the marine individuals.
The biota also has the distinction of producing Eastmanosteus pustulosus (the type species of that fearsome placoderm fish genus), some of the first trees (lycopsids and possible cladoxylopsids), and fossils of the rare tree-sized fungus, Prototaxites — the largest organism on land when it first appeared earlier in the Devonian.
Also of significance are occasional occurrences of exceptional preservation, such as the sarcopterygian…
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