For ten points, identify this geologic period occurring between the Ordovician and Devonian.
Parakidograptus acuminatus, a graptolite species, is an index fossil for the beginning of this period. Its major geologic events include the formation of the hematite-bearing Clinton Formation as a result of the erosion of the previous Taconic Orogen, as well as the beginning of the Caledonian orogeny, a spate of mountain-building in present-day England and Greenland. Divided into the Llandoverian, Wenlockian, Ludlovian, and Pridolian epochs, this period's biota included early vascular plants, myriapods, and eu-teryptids, which were giant sea scorpions. For ten points, identify this geologic period occurring between the Ordovician and Devonian.
Parakidograptus acuminatus, a graptolite species, is an index fossil for the beginning of this period.
Silurian period