STORY: Over the years, scientists combing the riverbeds of northern Alaska have found the bones of long-extinct dinosaurs. The bones have revealed clues to what the Arctic was like some 80 million years ago. But despite their constant searching, they've never found a good set of dinosaur footprints. That is, until now.
GANGLOFF: "Once you find some tracks and trackways, you find lots of them. That just seems to be the way it goes."
That's Roland Gangloff. He's the curator of earth sciences at the University of Alaska Museum in Fairbanks. This past summer, while floating the Colville River in northwestern Alaska, he and a team of researchers came across dinosaur tracks preserved in solidified mud and stone. The tracks were part of an extensive series of ancient trackways found at 13 sites along the river that were filled with dinosaur footprints. Roland Gangloff.
GANGLOFF: "Everything we see tells us that they are trampled surfaces. How many animals and what kinds we'll never be able to differentiate."
Some of the impressions were clear enough to show the rough, pebble-like texture of the dinosaur's foot. That's also a new find, says Roland Gangloff.
GANGLOFF: "It's the first time we've ever found that. And so far in the literature it may be exceedingly rare, and only certain dinosaurs may have these surface skin tubercles in the pad of the foot."
The tracks were mostly of three-toed dinosaurs--prehistoric creatures like the duckbilled dinosaur that were up to 43 meters in length. And one track was especially large, some 45 centimeters long. That one was most likely made by a smaller but still fearsome relative of Tyrannosaurus Rex. And while most dinosaurs had three toes, Roland Gangloff found one print with four toes.
GANGLOFF: "Our first-cut conclusions are that these are either ankylosaurus or ceratopsans--horned dinosaurs or armored dinosaurs--because they both have four-toed feet and tend to give more distinct digit impressions than some of the big sauropods."
Scientists say the trackways were most likely made in the very early Cretaceous period, some 90 to 110 million years ago. This finding is especially important because if scientists are right, it means dinosaurs roamed Alaska about 25 million years earlier than they previously believed.
GANGLOFF: "And we've predicted that we should find the very last populations of dinosaurs in the high Arctic areas. And we should also find some of the earliest evidence of some of the major lineages of dinosaurs that originated in Eurasia."
One hundred million years ago, Alaska's north slope was a whole lot different than it is today. The climate was much warmer, more like modern-day Northern California. Grasses, plants, even semitropical forests once flourished on a land that is now frozen tundra. Phillip Currie is a scientist at the Tyrell Museum of Paleontology in Alberta, Canada.
CURRIE: "Well, a hundred million years ago the Arctic of course was a much warmer place than it is today. That's not to say there weren't extremes of temperature in the winter months. Certainly when you have 24 hours of darkness you're in a situation when the temperature can drop pretty dramatically. Some of the geologic evidence that's been gathered in that region suggests that during the winter months it could fall below freezing. The big difference, though, is that there was no permanent ice cap. And because of that, plants could grow prolifically even well above the Arctic Circle."
Exactly why dinosaurs would want to spend much of their time in the high Arctic is a question researchers continue to puzzle over. One popular theory holds that Arctic dinosaurs had strong herding instincts--much like caribou do today--and that they migrated between summer and winter ranges. Only dinosaurs migrated on a much grander scale. Phillip Currie.
CURRIE: "During the summer months of course with all the plant material available for them to eat they had a good summer in smaller groups. But as the days started to shorten and started to get cooler and as you started to get the onset of night, I think these animals would start to collect into herds again, push south and end up overwintering in northern, central and southern Alberta."
Gangloff and his team of scientists from the University of Alaska campuses in Fairbanks and Anchorage collected casts and impressions of five different types of dinosaurs over the past summer. Those casts as well as other artifacts and photos are on display at the University of Alaska Museum in Fairbanks.
OUTRO: For Arctic Science Journeys, this is Doug Schneider, reporting from Fairbanks, Alaska.
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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