Five years ago, science made a great discovery: dinosaur bones of a new species in a riverbed in Alaska. The research group at the time gave the new species the Inupiat name “Old pasture-goer”, Ugrunaaluk kuukpikensis. But doubts remained as to whether the find was actually a new species. A new analysis of all bone finds now shows that it is probably not a new species of its own, but a juvenile of Edmontosaurus, a widespread genus of herbivorous duck-billed dinosaurs.
The international research group led by Ryuji Takasaki and Anthony Fiorillo concludes in its analysis of the cranial bones that the previous finds described as a new species, rather belonged to one of the two Edmontosaurus species, notabene to a juvenile. The researchers rely on the anatomical comparisons and phylogenetic analyses they had made on the parts. “While recent studies have shown that a new species of hadrosaurs (duck-billed dinosaurs) had been found in Alaska, our research shows that these Arctic dinosaurs belong to the genus Edmontosaurus, a common and recognized genus of duck-billed dinosaurs that once occurred from Canadian Alberta to northern Colorado,” explains Ryuji Takasaki.
Although the research group refutes the systematic division into a new species, the find is very remarkable. For one thing, there are not many dinosaur finds in the Arctic, mainly due to the strong glaciations over the course of millions of years. These have probably washed numerous fossils, if any, into the sea. On the other hand, the analyses show that the genus Edmontosaurushad spread much further north than previously thought. As a result, this dinosaur genus turns out to be ecological generalists. “In other words, Edmontosaurus was a very successful dinosaur that could adapt to a wide range of environmental conditions,” says Anthony Fiorillo. “It is not unrealistic to compare these with today’s bighorn sheep, wolves or pumas when it comes to spread and number.” The comparison with reindeer is also not wrong, since the dinosaurs were also herbivores and probably had to get through the cold seasons with lean food.
In their comparison, the researchers found another remarkable clue: The fossil finds closely resemble the fossils of a new species found on Hokkaido, Japan, Kamuysaurus. Takasaki and his colleagues suspect that the ancestor of the two species once had lived in Asia and then immigrated over time over the land bridge between Russia and North America. This would mean that Edmontosaurus‘ adaptations to the cold regions of what was then Alaska had first formed, and the animal had only then adapted to the warmer climate conditions further south. Ronald Tykoski of the Perot Museum in Dallas, USA, and co-author of the study, says the find was quite remarkable. But he also says: “The study is a perfect example of why paleontologists need to be careful and how individual growth and the life phase of a fossil find must be included into the analyses.” In any case, the find from northern Alaska shows that dinosaurs had a much greater adaptability than previously thought and they had also dominated the world in the Arctic.
Source: Perot Natural History Museum, Dallas (TX) / Takasaki et al (2020) PLOSOne EPub
Link to the scientific article: https://doi.org/10.1371/journal.pone.0232410