Massive herbivores are believed to have existed in the Triassic Period some 200 million years ago. What is strange about this finding is that large mammals should not be present at this point. Scientists believe that large mammals died at the end of the Permian Period 251.9 million years ago.
After this, only small mammals existed when dinosaurs became the dominant species on Earth, with mammals regaining crowns some 50 million years ago.
However, the discovery of large herbivores still found in southern Poland says that large mammals and large dinosaurs must coexist.
This creature was named Lisowicia bojani, and included the same evolutionary branch as mammals.
Grzegorz Niedzwiedzki, paleontologist at Uppsala University in Sweden who co-authored a paper published in the journal Science, said: "We used to think that after the Permian extinction ended, their mammals and relatives retreated into the shadows while dinosaurs rose and grew into large sizes."
The newly discovered animals were part of a family that was synodontized and lived at the same time as other sauropods, a group of dinosaurs that eventually led to long-necked diplodocus – one of the greatest creatures that ever walked on Earth.
Experts theorize that environmental factors during the Triassic Period might have caused gigantism throughout the world.
Christian Kammerer, a specialist who was synodont at the North Carolina Museum of Natural Sciences, said Lisowicia's size was "shocking".
"Big dicynodonts have been known before in Permian and Trias, but never on this scale.
"Overall I think this is a very interesting and important paper, and shows us that there is still much left to be learned about the relatives of the early mammals in the Trias."