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

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. The Bulmanicrusta? sp. specimens contain numerous graptoblasts (small, thick-walled vesicles) in organic connection with the colony. These were not pathological features, but probably were resting cysts produced by the crustoid colony as a normal part of its life cycle. Their presence supports the interpretation that the Caesar Creek crustoid was adapted to ephemeral or disturbance-prone environments. -from Authors