New dinosaur track-site discovered in Alaska

Paleontologist have discovered a remarkable new track-site filled with duck-billed dinosaur footprints in Alaska's Denali National Park.
The finding demonstrates the duck-billed dinosaurs - referred to as hadrosaurs - not only lived in multi-generational herds but thrived in the ancient high-latitude, polar ecosystem, researchers said.
"Denali is one of the best dinosaur footprint localities in the world. What we found that last day was incredible - so many tracks, so big and well preserved," said lead author Anthony R Fiorillo, curator of Earth sciences at the Perot Museum of Nature and Science.
"Many had skin impressions, so we could see what the bottom of their feet looked like. There were many invertebrate traces - imprints of bugs, worms, larvae and more - which were important because they showed an ecosystem existed during the warm parts of the years," said Fiorillo.

The discovery of a new track-site of mostly hadrosaurid dinosaur footprints provides insight into the herd structure and behaviour of northern polar dinosaurs and perspective on populations of large-bodied herbivores in an Arctic greenhouse world.
"This track-site occurs in the Upper Cretaceous Cantwell Formation in the Alaska Range, and it is the largest track-site known from this far north," Dr Yoshitsugu Kobayashi of Hokkaido University Museum, Japan and co-authors wrote in a paper published in the journal Geology.
Preservation of the track-site is exceptional: most tracks, regardless of size, contain skin impressions and they co-occur with well-preserved plant fossils and invertebrate trace fossils of terrestrial and aquatic insects.

Statistical analyses of the tracks show that individuals of four different age classes of hadrosaurids lived together in a large social group.