A study finds evidence of dispersal of dinosaurs that coincides with a dip in atmospheric CO2 levels, suggesting prior climatic barriers to dispersal. Although the earliest known herbivorous sauropodomorph dinosaurs appeared in the Southern Hemisphere in the late Triassic, around 230 million years ago, and their land travel across Pangea was likely unimpeded, the dinosaurs did not appear in the Northern Hemisphere for 15 million years, possibly due to climatic barriers. Dennis V. Kent and Lars B. Clemmensen constructed a timeline of the magnetic signatures in the Fleming Fjord Group of rock formations in East Greenland to synchronize the geological time scale of the rocks with other late Triassic fossil-bearing sequences around the world. Using the time scale, the authors found that the sauropodomorphs' earliest known appearance in their northernmost range was around 214 million years ago, coinciding with a major dip in atmospheric CO2 between 215 and 212 million years ago. Prior to the decline in CO2, tropical desert belts were intensely arid, and equatorial humid belts were unstable, possibly forming climatic barriers that prevented previous sauropodomorph dispersal. According to the authors, fossil records of carnivorous theropod dinosaurs suggest that their dispersal was sporadic and may not have been subject to the same climate constraints.
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Article #20-20778: "Northward dispersal of dinosaurs from Gondwana to Greenland at the mid-Norian (215-212 Ma, Late Triassic) dip in atmospheric pCO2," by Dennis V. Kent and Lars B. Clemmensen.
MEDIA CONTACT: Dennis V. Kent, Lamont-Doherty Earth Observatory, Palisades, NY; email: < dvk@ldeo.columbia.edu >
Proceedings of the National Academy of Sciences