Late Middle Ordovician Graptolites from the Subsurface of Eastern Nebraska

Graptolite rhabdosomes identified as Climacograptus typicalis var. crassimarginalis Ruedemann & Decker were obtained from a dolomite core in eastern Nebraska. The occurrence of this graptolite suggests a late Middle Ordovician (late Wilderness-Trenton) age for the rocks bearing it. This and other occurrences of this species support an interpreted widespread distribution of carbonates of this age in the continental interior. Flanges projecting from the genicular angle of the thecae of these graptolites may have aided flotation in warm shallow seas and permitted wide distribution in carbonate environments.