Dinosaurs were southerners. The famous group dominated the world for tens of millions of years and , which has led to some confusion over where the very first dinosaurs were born. Two new studies pile on the evidence that the earliest dinosaurs lived in South America or one of the other southern continents.
When the first dinosaurs appeared, roughly 240 or 250 million years ago, Earth鈥檚 continents were united in the supercontinent Pangaea. In principle dinosaurs could have arisen in any corner of Pangaea. However, given that many of the earliest dinosaur fossils have been unearthed in South America, Africa and other regions that formed southern Pangaea, palaeontologists have begun to suspect that this region was the cradle of dinosaur evolution.
Last year, though, a high-profile study suggested an alternative. A team of British palaeontologists led by Matthew Baron at the University of Cambridge argued for the most radical overhaul of the dinosaur evolutionary tree in 130 years. In their new tree, some of the fossils that lie closest to the base of the dinosaur group come from Europe 鈥� such as one called Saltopus that was found in Scotland. The team said this might suggest the dinosaur cradle was in northern Pangaea.
Advertisement
Now, a team led by J煤lio Marsola at the University of Sao Paulo, Brazil, has looked at the subject in more detail. They examined six dinosaur evolutionary trees published over the last 20 years 鈥� including the radically different one published last year. Then they looked at the geographical distribution of the species near the base of the dinosaur family in each tree. Almost without exception, the evolutionary trees suggest dinosaurs came from southern Pangaea.
Surprisingly, even last year鈥檚 radically different dinosaur tree favours a southern birthplace. Although Baron and his colleagues emphasised that northern fossils like Saltopus plot out near the base of the dinosaurs, their evolutionary tree actually shows that these northerners were the exception rather than the rule: most of the fossils that fall near the base of their modified dinosaur group are southerners.
鈥淥ur results greatly support the Southern hypothesis as the most plausible, given our current understanding,鈥� says Marsola. 鈥淣ot only that, our result didn鈥檛 yield any indication of a possible [northern] origin for the group.鈥�
One of Marsola鈥檚 co-authors is Richard Butler at the University of Birmingham, UK. He points out that Baron鈥檚 team independently published their own analysis of dinosaur origins this week 鈥� and also overturned their northern dinosaur idea. Baron and his colleagues concluded there is a 99 per cent chance dinosaurs came from South America, and an 83 per cent chance they came from the very southernmost part of that continent.
Neither team knew about the work that the other team was doing, says Butler. 鈥淚n any case, even [Baron鈥檚 team] accept that a southern origin is by far the most likely.鈥�
