Aeronian

In the geologic timescale, the Aeronian is an age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that began 440.5 ± 1.0 Ma and ended 438.6 ± 1.0 Ma (million years ago). The Aeronian Age succeeds the Rhuddanian Age and precedes the Telychian Age, all in the same epoch.

glaciation

Calymene is a genus of trilobites in the order Phacopida, suborder Calymenina, that are found throughout North America, North Africa, and Europe in primarily Silurian outcrops. Calymene is closely related to Flexicalymene, and both genera are frequently found enrolled. Calymene trilobites are small, typically 2 cm in length. The cephalon is the widest part of the animal and the thorax usually has 13 segments.