| Noun | 1. | Carboniferous period - from 345 million to 280 million years ago Paleozoic, Paleozoic era - from 544 million to about 230 million years ago Pennsylvanian, Pennsylvanian period, Upper Carboniferous, Upper Carboniferous period - from 310 million to 280 million years ago; warm climate; swampy land Lower Carboniferous, Lower Carboniferous period, Missippian period, Mississippian - from 345 million to 310 million years ago; increase of land areas; primitive ammonites; winged insects |