MOST geologists agree on the placement of the continents at the end of the Cretaceous. Palaeobiologists, however, hold divergent opinions1,2. Some workers connect South America to Africa, some connect it only to North America, while others isolate South America totally. New evidence from vertebrate palaeontology suggest that a substantial land connection between North and South America existed 85-100 Myr ago which facilitated the passage of many terrestrial vertebrates between the continents, including large herbivorous dinosaurs. Specimens of hadrosaurian dinosaurs, collected in the first half of the present century, have now been used to reanalyse not only the palaeobiogeography but also the classification and phylogeny of this group. 1 report here the first solid evidence of an extensive land connection for large terrestrial vertebrates of this sort between North and South America at the end of the Cretaceous.