Scientists have an ancient mystery on their hands: the massive flight of dinosaurs out of Europe.
The migration goes one way -- out of the continent -- and lasted for 25 million years with no dinosaurs filtering back in, the Telegraph reported.
So far, researchers who used a novel method to posit the ancient migration can't find any discernible reason why dinosaur families packed up their things and high-tailed it out of Europe.
For all they know, it could be a blank spot in the fossil record, the Christian Science Monitor reported.
To discover this blank spot and theorize that a one-way migration way is to blame, researchers used a tool they've tried before to illuminate the ancient movement of dinosaurs around Europe: network theory.
Network theory has been employed to chart online trends and social chatter and "is the practice of using graphs to depict certain relationships," as the Monitor described it. Since this is the first time it's been used to track dinosaurs, researchers hope that the method can be applied to other fields in the future."Network theory has been studied in physics for a number of years, however it is finally permeating into other disciplines," said researcher James Scibberas. "This idea that most things can, and should, be considered in the context of the whole system will lead to some exciting new findings in a wide range of fields."
For data, they turned to the Paleobiology Database, which contains every single accessible dino fossil found and documented in the world. The records date from the upper Triassic to the late Cretaceous period -- a period of 180 million years.
In those records, scientists were looking for connections between Europe and other continents: the same dino families across time and space. Researchers applied a filter to the database so that only the first occurrence of a dinosaur family connection would be pinpointed. This was done to account for the fact that some regions have exhaustive fossil records, while others remain unexplored and therefore sparse.
Researchers applied network theory to this data to determine how dinosaurs moved about Europe during that time, specifically a period of 225 million years ago to 65 million years ago.
They found hints of a huge migration in the middle of that span of time. During the Early Cretaceous period -- 125 to 100 million years ago -- the connections were all outgoing, hinting at a massive migration out of Europe. The same types of dinosaurs were found on different continents in different generations, suggesting this pattern of movement.This migration continued after "supercontinent" Pangea broke up 175 million years ago, creating land masses separated by oceans. After that, dinosaurs found land bridges and kept moving out of Europe into the new world beyond, but at a fairly slow pace.
"We presume that temporary land bridges formed due to changes in sea levels, temporarily reconnecting the continents," said researcher Dr. Alexander Dunhill. "Such massive structures – spanning, for example, from Indo-Madagascar to Australia – may be hard to imagine. But over the timescales that we are talking about, which is in the order of tens of millions of years, it is perfectly feasible that plate tectonic activity gave rise to the right conditions for such land bridges to form."
Scientists always believed that the creatures migrated all over the world after the split of Pangea, and this research hints that they did after all.
But the most interesting find in the study was evidence that the migration was an exodus: dinosaurs moved out of Europe but none came back in for 25 million years. They eventually returned.
Dunhill can't account for this pattern yet, but it's possible an incomplete fossil record is to blame.
"It might be a real migratory pattern or it may be an [artifact] of the incomplete and sporadic nature of the dinosaur fossil record," he said.
[Image via boscorelli/Shutterstock]