April 26, 2016

Aim: To reconstruct dinosaur macro-biogeographic patterns through the Mesozoic Era using a network-based approach. We test how continental fragmentation affected dinosaur macro-biogeographic structure and evolutionary rates.

Location: A global occurrence database of dinosaur families from the Late Triassic to the end-Cretaceous was used for this study.

Methods: Biogeographic and geographic network models were constructed. Continental landmasses were linked by direct continental contact and sea level conditioned connections in geographic networks, and by shared dinosaur families in biogeographic networks. Biogeographic networks were run with raw, novel and first-step connections for all dinosaur, ornithischian, theropod, and sauropodomorph taxa.

Results: Geographic connectedness declines through time, from peak aggregation in the Triassic-Jurassic to complete separation in the latest Cretaceous. Biogeographic connectedness shows no common trend in the raw and novel connection network models, but decreases through time whilst showing some correlation with continental fragmentation in most of 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 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. Main conclusions There is some evidence to suggest that dinosaur macro-biogeographic structure was influenced by continental fragmentation, although intercontinental exchange of dinosaur faunas appears to have 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.