Study Finds Dinosaur Families|Fled Europe, Never to Return


(CN) — Dinosaur families migrated away from Europe even after continents drifted apart following the separation of the supercontinent Pangea, according to a study published this week in the Journal of Biogeography.
     The researchers documented a trend of dinosaurs spreading to the other six continents, with none returning or coming into Europe.
     Alex Dunhill, one of the authors of the study, said in an email that while his team’s findings indicate that there was a dinosaur exodus from Europe during the Early Cretaceous period — 100 to 125 million years ago — it’s unclear what sparked this trend.
     “It is possible that this could be a real pattern, and Europe witnessed a burst of speciation — a lineage-splitting event that produces two or more separate species — during this time period and then these families spread across the world,” Dunhill said. “However, it is likely this pattern is brought about by the varying quality of the dinosaur fossil records, both in terms of geography and geological time.”
     Using the Paleobiology Database — which contains every documented dinosaur fossil from around the world — the researchers cross-mapped fossil records for dinosaur families from different continents with different periods of time to determine how they migrated.
     The researchers applied a filter to the database records to account for disparities in fossil records between different continents, partly due to some areas being researched more extensively than others. The filter only counted the first instance of a dinosaur family connection occurring between two continents.
           “The results show that dinosaur families were still moving around the world, with populations migrating between continents, even when major continental landmasses were isolated and sea levels were exceptionally high,” Dunhill said.
     This led researchers to believe that long, temporary land bridges formed, which enabled dinosaurs to migrate to different continents.
     “There have been other studies that have suggested this may be the case, but this is the first using this particular method,” Dunhill said. “Although this migration reduced as the continents separated, it doesn’t stall all together as you might imagine it would when you have vast oceans between landmasses.”
     The team used network theory — which is used in computer science to establish connections between similar content or people such as friend suggestions on Facebook or search results on Google — to measure evolutionary rates for different dinosaurs, while also comparing the strength of patterns over specific time periods.
     “The whole study is based around networks. We have networks of nodes and edges, our nodes are our continents and our edges are the dinosaur families that are shared between our continents. Therefore, if a dinosaur family occurs on two different continents, we draw a line, i.e. an edge, connecting the two,” Dunhill said.
     Future research will likely involve incorporating a dinosaur phylogeny into the existing networks.
     “A phylogeny is an evolutionary tree, kind of like a family tree, that will allow us to work at a finer level of detail than we can when just working with dinosaur families,” Dunhill said. “We have plans to roll out the network method for a number of other studies, but I don’t want to give too much away right now!”
     
     Map credit: Alex Dunhill, University of Leeds

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