Related by context. Frequent words. (Click for all words.) 62 Cretaceous Period 61 Late Cretaceous 60 Pleistocene 56 Quaternary 56 Cambrian explosion 56 Mesozoic 55 Eocene 55 interglacial period 55 Carboniferous 55 fossils 55 Cretaceous 54 Pleistocene era 54 trilobites 53 interglacial 53 Paleocene 53 Ordovician 53 subarctic 53 H. erectus 53 Precambrian 53 tetrapod 52 glaciation 52 marine reptiles 52 prehistoric 52 hominid 52 Tiktaalik 52 Burgess Shale 51 Younger Dryas 51 Pliocene 51 stromatolites 51 fossil 51 Holocene 51 diatom 51 hominins 51 terrestrial ecosystems 50 dinosaurs 50 supercontinent 50 landforms 50 foraminifera 50 plesiosaur 50 Beringia 50 megafauna 50 dinosaurs roamed 49 volcanism 49 Homo sapiens 49 limestone cave 49 Poinar 49 continental crust 49 marine invertebrates 49 crocodilians 49 Homo erectus 49 diatoms 49 Australopithecus 49 tetrapods 49 microfossils 49 marine sediments 49 planktonic 48 Polar Regions 48 Paleozoic 48 fossilized remains 48 Paleolithic 48 millenniums 48 lavas 48 basaltic 48 prehistory 48 Jurassic 48 Ice Age 48 hominids 47 plate tectonics 47 biogeography 47 Fossils 47 fossilized bones 47 sauropods 47 mammoths 47 palaeontology 47 prokaryotes 47 oceanic crust 47 methane hydrate 47 hominin 47 Triassic 47 volcanic crater 47 theropod 47 single celled organisms 47 limestone caves 47 mass extinction 47 Homo habilis 47 genus Homo 47 zircons 46 sauropod 46 tyrannosaur 46 sediment cores 46 Australopithecus afarensis 46 solar nebula 46 multicellular 46 Proterozoic 46 degrees Fahrenheit warmer 46 anatomically modern 46 atmospheric methane 46 Miocene 46 fossilized 46 middens 46 Prehistoric