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In situ crustoid graptolite colonies from an Upper Ordovician hardground, southwestern Ohio

Published online by Cambridge University Press:  20 May 2016

Charles E. Mitchell
Affiliation:
1Department of Geology, State University of New York at Buffalo, Buffalo 14260
Mark A. Wilson
Affiliation:
2Department of Geology, the College of Wooster, Wooster, Ohio 44691
James M. St. John
Affiliation:
2Department of Geology, the College of Wooster, Wooster, Ohio 44691

Abstract

In situ colonies of Bulmanicrusta? sp. encrusting the surface of a hardground from the Upper Ordovician Bull Fork Formation provide the first glimpse of the full colony form, habitat, and faunal associates of a crustoid graptolite. Bulmanicrusta? sp. exhibits a runner-type colony form suited to rapid expansion over hard substrates, indicating it was an opportunistic member of the hardground community. This community also included two bryozoans (“Proboscina” and Amplexopora), Cornulites, and crinoids. The Bulmanicrusta? sp. specimens contain numerous graptoblasts (small, thick-walled vesicles) in organic connection with the colony. These objects are located at branch termini and confirm that graptoblasts were not pathological features, but probably were resting cysts produced by the crustoid colony as a normal part of its life cycle. Thus, the presence of graptoblasts supports the interpretation that the Caesar Creek crustoid was adapted to ephemeral or disturbance-prone environments.

Information

Type
Research Article
Copyright
Copyright © The Paleontological Society 

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