Related by context. Frequent words. (Click for all words.) 67 Cretaceous Period 61 Carboniferous 61 Late Cretaceous 60 Cretaceous 59 Pliocene 59 Pleistocene 59 Triassic 58 Precambrian 58 interglacial 58 Mesozoic 57 Eocene 57 Paleozoic 56 dinosaurs roamed 56 Ordovician 56 Quaternary 55 prehistory 54 glaciation 53 Holocene 53 trilobites 52 Medieval Warm Period 51 prehistoric 51 Fertile Crescent 51 continental drift 51 geologic 50 Proterozoic 50 Little Ice Age 50 epochs 50 Oligocene 50 millenniums 49 marine sediments 49 mass extinctions 49 megafauna 49 dinosaurs 49 sedimentary rock 49 Jurassic 48 lake sediments 48 Devonian 48 geologically 48 Miocene 48 Silurian 47 multicellular organisms 47 plate tectonics 46 mass extinction 46 earth crust 46 Ice Age 46 tyrannosaur 46 epoch 46 Paleolithic 46 fossils 46 eons 46 terrestrial ecosystems 46 paleo 46 equinoxes 45 fossil 45 multicellular 45 Tiktaalik 45 volcanism 45 lithosphere 45 caldera 45 mammoths 44 paleontological 44 Tibetan Plateau 44 tyrannosaurs 44 magmatic 44 Mammoths 44 baleen whales 44 sediment cores 44 fossilized remains 44 Homo sapiens 44 moraines 44 single celled organisms 44 radiocarbon dating 44 Han Dynasty 43 Fossils 43 crustal 43 millennia 43 martian 43 radiocarbon 43 Mesoamerica 43 thermocline 43 sedimentary rocks 43 atmospheric carbon dioxide 43 tetrapods 43 fossilized 43 Archean 43 vertebrate species 43 basalts 43 single celled 42 extinctions 42 hominins 42 glacial 42 Earth crust 42 #BC [003] 42 Industrial Revolution 42 storminess 42 landmasses 42 anatomically modern 42 diatoms 42 sediments 42 glaciers 42 Neolithic