Polar dino tracks show full ecosystem

by Allison Mills
Monday, November 3, 2014

Researchers recently uncovered a new dinosaur tracksite in Alaska’s Denali National Park. The well-preserved Late Cretaceous footprints were left by duck-billed dinosaurs called hadrosaurs. Most of the tracks are incredibly detailed, and some even show some skin impressions; they represent animals of various ages. Given the wealth of data, the tracks provide insight into the herd dynamics and paleobiology of the greenhouse-world Arctic.

Despite the latitude, the Arctic during the Late Cretaceous was relatively warm and boasted many more trees than it does now. Prior studies have shown there was still winter sea ice, but that it may have been intermittent. Despite the cold, this new tracksite and a study describing it published in Geology support a growing body of research that suggests polar hadrosaurs were year-round residents living in herds that included adults, subadults, juveniles and even some infants. The track size differences between ages — sorted from hundreds of impressions on a steeply dipping plane about 180 meters long by 60 meters wide — support the idea that hadrosaur young went through an early growth spurt.

“The hadrosaur tracks show specifically where they lived and how they acted as an extended family,” said lead author Anthony Fiorillo, curator of earth sciences at the Perot Museum of Nature and Science in Dallas, Texas, in a statement. “To find evidence of a big dinosaur population proves once again that the ecosystem of the ancient Arctic was a very different place than we might once have thought.”

The track-bearing rock layer also bears other trace fossils. “There were many invertebrate traces — imprints of bugs, worms, larvae and more,” which are “important because they showed an ecosystem existed during the warm parts of the year,” Fiorillo said.

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