DINOSAUR BIOGEOGRAPHIC STRUCTURE AND MESOZOIC CONTINENTAL FRAGMENTATION: A NETWORK-BASED APPROACH

Dinosaur macro-biogeographic structure is influenced by continental fragmentation, although some intercontinental exchange of dinosaur faunas continued up to the end of the Cretaceous. Macro-biogeographic patterns are obscured by uneven geographic sampling through time and a residual earlier Mesozoic distribution which is sustained up to the end of the Cretaceous. Here, we use a novel network-based approach to reconstruct dinosaur macro-biogeographic patterns through the Mesozoic Era and test how continental fragmentation affected dinosaur macro-biogeographic structure and evolutionary rates. Biogeographic networks were run with raw, novel, and first-step connections for all dinosaur, ornithischian, theropod, and sauropodomorph taxa. Geographic connectedness declines through time, from peak aggregation in the Triassic-Jurassic to complete separation in the latest Cretaceous. Biogeographic connectedness shows no trend in the raw and novel connection network models, but decreases through time whilst showing some correlation with continental fragmentation in the first-step network models. Despite continental isolation and high sea levels, intercontinental faunal exchange continued right up to the end of the Cretaceous. Continental fragmentation and dinosaurian macro-biogeographic structure do not share a common pattern with dinosaurian evolutionary rates, although there is some evidence that increased continental isolation resulted in increased origination rates in some dinosaurian lineages. Spatiotemporal sampling biases and early Mesozoic establishment of family-level distribution patterns are important drivers of apparent dinosaur macro-biogeographic structure.