Read aloud Over 200 million years ago, massive volcanic eruptions led to the extinction of the dinosaur's most important competitors, thus enabling their rise to become rulers of the earth. This is what scientists from an international research team found out when analyzing layers of rock. The discovered fossils in solidified lava flows and in sediments indicate that the climatic changes associated with the volcanic eruptions largely wiped out the so-called crurotarsi, relatives of today's crocodiles. The competing dinosaurs, however, survived the disaster unscathed and then reached their later size and distribution. That the dinosaurs could better adapt to the volcanic eruptions, was probably pure coincidence, write Jessica Whiteside and her colleagues from the Brown University in Providence. Just over 200 million years ago, the land masses of Earth formed the vast continent of Pangea. The dominant animals of the time were the Crurotarsi, crocodile-like reptiles. They had a much higher biodiversity than the competing dinosaurs, which at that time also reached only a small size. With the breakup of Pangea, however, the living conditions changed massively: huge streams of lava flowed out of the created fissures and volcanoes released large quantities of gas into the atmosphere. The volcanic eruptions lasted about 600, 000 years and the solidified lava finally covered an area almost as big as the USA.

Researchers focused their analysis on a number of well-known sites in the area to find out what had happened to animals and plants during the disaster. Plant and pollen findings in dated volcanic rock layers showed that half of all plants had disappeared at the end of the volcanic period. In addition, in the younger rock layers, unlike the older deposits no footprints of Crurotarsi more. On the other hand, footprints of dinosaurs could still be detected in the sediments deposited after mass extinction? yes, even significantly larger impressions than before. Consequently, the dinosaurs had survived the volcanic eruptions and then even increased in size.

But why did the dinosaurs survive the catastrophe while exterminating the diverse Crurotarsi and numerous other species? There is no simple explanation for this: "Apparently the dinosaurs were fortunate enough to be particularly well adapted to the special climatic conditions, " says Whiteside. The study also shows that in evolution not always prevails in the direct competition superior way, but sometimes simply random rules.

Jessica Whiteside (Brown University, Providence) et al .: PNAS ddp / science.de? Thomas Neuenschwander advertisement

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