Cretaceous Continental Bridges, Insularity, and Vicariance in the Southern Hemisphere: Which Route Did Dinosaurs Take?

Abstract

The history of dispersal of biota during the Mesozoic in the southern hemisphere is much debated. Clearly, the sequential break-up of Gondwana produced physical barriers that must, variously, have hampered dispersal events, and therefore impacted the phylogenetic hypotheses. Did various terrestrial organisms undergo dispersal via recently claimed continental bridges? When were the geographic and environmental conditions at an optimum for diffusion during Mesozoic times? Dinosaurs are arguably the most relevant group for illuminating the biogeography of the southern landmasses during the Cretaceous. Their vast stratigraphic and geographic occurrence is intimately linked to the evolution of Gondwana. Recent discoveries from all southern landmasses challenge several vicariant models. This study summarizses the most significant geologic, palaeogeographic, palaeontologic, and phylogenetic data on Cretaceous Gondwanan dinosaur evolution, with particular emphasis on the ephemeral land bridges that bulk large in recently developed biogeographic models. Comparison between different datasets accords with a complex and sequential mix of vicariance and dispersal patterns characterizing the fabric of dinosaurian faunas at that time. This study probes the significance of ephemeral intercontinental connections with regard to the biotic dispersal in the Late Cretaceous. An earlier peak in dinosaur diversity and dispersals seems likely.