Cretaceous South America Argentina 89 Neuquen Basin 39 Patagonia 37 taxonomy 24 biostratigraphy 23 Andes 22 Ammonoidea 20 paleoenvironment 19 Bivalvia 17 Western Hemisphere 17 World 17 morphology 16 paleoecology 16 paleomagnetism 16 bivalve 15 Lower Cretaceous 14 Neuquén Basin 14 Paleogene 14 fossil 14 geochronology 14 Chile 13 Late Cretaceous 13 ammonite 13 Ostreidae 12 fossil record 12 Neuquen 11 Early Cretaceous 10 Ostracoda 9