The massive herbivore is believed to have existed in the Triassic Period some 200 million years ago. What is odd about the finding is that large mammals were not supposed to have existed at this point. Scientists had believed that large mammals died out at the end of the Permian Period 251.9 million years ago.
After this, only smaller mammals existed as the dinosaurs became the dominant species on Earth, with mammals regaining the crown about 50 million years ago.
However, the discovery of the huge herbivore remains found in southern Poland say that large mammals and large dinosaurs must have coexisted.
The creature has been named the Lisowicia bojani, and belonged to the same evolutionary branch as mammals.
Grzegorz Niedzwiedzki, a palaeontologist at Uppsala University in Sweden who co-authored the paper published in the journal Science, said: “We used to think that after the end-Permian extinction, mammals and their relatives retreated to the shadows while dinosaurs rose up and grew to huge sizes.”
The newly discovered beasts are part of the dicynodont family and lived at the same time as other sauropods, a dinosaur group which eventually led to the long-necked diplodocus – one of the largest creatures to have ever walked the Earth.
Experts theorise that environmental factors during the Triassic Period may have led to gigantism across the globe.
Christian Kammerer, a dicynodont specialist at the North Carolina Museum of Natural Sciences, said the size of Lisowicia was “startling”.
“Large dicynodonts have been known before in both the Permian and the Triassic, but never at this scale.
“Overall I think this is a very intriguing and important paper, and shows us that there is a still a lot left to learn about early mammal relatives in the Triassic.”