Tracks of two prehistoric birds found in Alaska

Fossilised tracks from two newly discovered prehistoric birds have been found in Alaska's Denali National Park, according to findings released by an expert in Arctic palaeontology.

The previously unknown birds were among a wide variety of birds that left fossilised tracks in Denali, Tony Fiorillo, a palaeontologist and curator at the Museum of Nature and Science in Dallas, said in an interview.

"The skies over Denali were a pretty busy place," he said.

The birds are considered new species and now have names given by Fiorillo and his team -- "Magnoavipes denaliensis," incorporating the park's name for a bird that left especially large tracks, and "Gruipeda vegrandiunis," roughly translating to "tiny one," for a bird that left small tracks.

Fiorillo, lead researcher on the project, published his findings in the current issue of the Journal of Systematic Paleontology. Previous research determined that pterosaurs -- flying winged reptiles -- also dwelled during the Cretaceous period in what is now Denali, he said.

Denali National Park, one of the most popular visitor destinations in Alaska, is also drawing increased attention from palaeontologists.

Because of the characteristics of the rock formations there, Denali has proven to be one of the best places in the world to find prehistoric bird tracks, Fiorillo said.

Thousands of prehistoric bird tracks have been found there, but what is particularly important is the variety.

"It's the most biodiversity represented by the tracks (in the world)," he said.

Some of the tracks match species that dwelled during that period in more southern latitudes of North America or in Asia -- suggesting birds migrated from great distances to Alaska to breed and nest in Cretaceous summers just as they do today.

"Isn't it kind of neat to think about the idea that in the Cretaceous, 70 million years ago, Alaska might have served the same kind of avian needs that it does today?" Fiorillo said.

Fiorillo has been conducting palaeontological digs in search of prehistoric bird tracks in Denali since 2006 and has been examining other fossils in the park since before then.

He helped discover the first dinosaur track in the park in 2005, which happened to be in a location close to the park road that carries busloads of summer tourists.

Along with birds, hadrosaurs -- duckbilled, plant-eating dinosaurs -- were plentiful in Alaska during the Cretaceous period, according to his research.

Fiorillo and colleagues from the University of Texas and the University of Alaska Fairbanks calculate that Alaska held about 500,000 hadrosaurs at any given time during that period -- roughly equivalent to modern caribou populations in Alaska.

The findings were presented at an American Geophysical Union conference held last month in San Francisco.

The climate at the time in the now-frigid region was fairly mild, "somewhere between annual temperatures of Calgary and that of Portland, Oregon," Fiorillo said. The land was well vegetated, with forests as well as open areas, he said.

The methane produced from the hadrosaurs, each of which emitted about 10 times as much of the gas as a modern cow, combined to create a small greenhouse effect and incrementally warm the region, the research speculates.

Fiorillo and his research partners believe the hadrosaurs also helped maintain the open spaces in the vegetation.