Related by context. Frequent words. (Click for all words.) 67 Late Cretaceous 65 Ordovician 64 Carboniferous 63 Cretaceous Period 60 Triassic 60 Pliocene 60 Eocene 59 Paleocene 59 Cretaceous 59 trilobites 59 marine sediments 58 Pleistocene 58 Precambrian 57 interglacial 57 taxa 57 Paleozoic 57 Mesozoic 57 interglacial period 57 supercontinent 56 Quaternary 56 glaciation 56 Younger Dryas 56 Proterozoic 56 basalts 56 terrestrial ecosystems 55 Oligocene 55 diatoms 55 Devonian 55 Lower Cretaceous 54 Tiktaalik 53 Medieval Warm Period 53 anoxic 53 Holocene 53 multicellular 53 Archaea 53 crocodilians 53 archaea 52 mass extinctions 52 megafauna 52 benthic 52 atmospheric CO 52 tetrapods 52 continental crust 52 vertebrate species 52 multicellular organisms 51 Miocene 51 marine invertebrates 51 microfossils 51 calcareous 51 Little Ice Age 51 diatom 51 clades 51 magmatic 50 marine reptiles 50 vertebrates 50 Archaeopteryx 50 single celled 50 solar nebula 50 clade 50 biogeography 50 mass extinction 50 species 50 lavas 50 lake sediments 50 amphibian species 50 sedimentary rocks 50 volcanism 49 abundances 49 theropod 49 baleen whales 49 olivine 49 dinosaurs roamed 49 basaltic 49 geologic 49 coral species 49 paleo 49 biogenic 49 decadal 48 eukaryotes 48 lithosphere 48 biota 48 facies 48 mammals 48 Ardipithecus 48 arthropods 48 oceanic crust 48 theropods 48 biosphere 48 biodiversity hotspots 48 sedimentary rock 48 Jurassic 48 phylogenetic 48 sedimentary 48 eukaryotic 48 zooplankton 47 Silurian 47 hominins 47 plesiosaur 47 vertebrate 47 Australopithecus 47 volcanic islands