Duck-billed Dinosaurs Endured Long, Dark Polar Winters Say Scientists
Posted on May 14, 2012
Researchers have discovered that duck-billed dinosaurs, known as hadrosaurs, opted to endure long, dark polar winters instead of migrating to more southern latitudes. Scientists say the bones of these dinosaurs indicate that survival during these tough winters was not easy for the hadrosaurs. The scientists have not yet provided theories as to how the duck-billed dinosaurs managed to survive these frigid winters.
Anthony Fiorillo, a paleontologist at the Museum of Nature and Science, excavated Cretaceous Period fossils along Alaska's North Slope. Most of the bones (like the one pictured above) belonged to Edmontosaurus, a duck-billed herbivore, but some others such as the horned dinosaur Pachyrhinosaurus were also found.
Fiorillo hypothesized that the microscopic structures of these dinosaurs' bones could show how they lived in polar regions. He enlisted the help of Allison Tumarkin-Deratzian, an assistant professor of earth and environmental science, who had both expertise and the facilities to create and analyze thin layers of the dinosaurs' bone microstructure. Another researcher, Anusuya Chinsamy-Turan, a professor of zoology at the University of Cape Town, was independently pursuing the same analysis of Alaskan Edmontosaurus fossils. When the research groups discovered the similarities of their studies, they decided to collaborate and combine their data sets. Half of the samples were tested and analyzed at Temple and the rest were done in South Africa.
Tumarkin-Deratzian says, "The bone microstructure of these dinosaurs is actually a record of how these animals were growing throughout their lives. It is almost similar to looking at tree rings."
The researchers found bands of fast growth and slow growth that seemed to indicate a pattern. The researchers questioned what was causing the dinosaurs to be under stress at certain times during the year: staying up in the polar region and dealing with reduced nutrition during the winter or migrating to and from lower latitudes during the winter. They did bone microstructure analysis on similar duck-billed dinosaur fossils found in southern Alberta, Canada, but didn't see similar stress patterns, implying that those dinosaurs did not experience regular periodic seasonal stresses. Since the Alaska fossils had all been preserved in the same sedimentary horizon, Fiorillo examined the geology of the bonebeds in Alaska where the samples were excavated and discovered that these dinosaurs had been preserved in flood deposits.
Fiorillo says, "They are very similar to modern flood deposits that happen in Alaska in the spring when you get spring melt water coming off the Brooks Mountain Range. The rivers flood down the Northern Slope and animals get caught in these floods, particularly younger animals, which appear to be what happened to these dinosaurs. So we know they were there at the end of the dark winter period, because if they were migrating up from the lower latitudes, they wouldn't have been there during these floods."
The findings, "Hadrosaurs Were Perennial Polar Residents," was published here in the April issue of The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology by researchers from University of Cape Town, Museum of Nature and Science in Dallas and Temple University.