When they think of dinosaurs, most people imagine them crashing through steaming jungles or wading in sultry tropical swamps. Yet according to former Earthwatch-supported Australian scientists Drs. Tom Rich (Museum Victoria) and Patricia Vickers-Rich (Monash University), a diversity of dinosaurs also thrived in cold polar areas during the Jurassic and Cretaceous periods.
Principal investigators of Earthwatch's Dinosaurs of Darkness project from 1986 to 1991, Rich and Vickers-Rich published a summary of their findings in a recent Science article with colleague Roland Gangloff (University of Alaska Museum). The article, called "Polar Dinosaurs," provides a valuable survey of dinosaur adaptations to extreme environments.
"The adaptations to extreme conditions provide us with insights into the physiological limits of dinosaurs that could never be gained by study, no matter how prolonged, of low latitude dinosaurs," said Rich. "They were clearly coping well with winter cold near the poles and prolonged periods of continuous darkness."
"Polar Dinosaurs" presents a comprehensive survey of all the dinosaur finds in historically polar regions, including Alaska, northern Canada, Siberia, Antarctica, Australia, and New Zealand. Southeastern Australia, which was within the Antarctic Circle during the early Cretaceous, and has the most diverse polar dinosaur fauna found so far.
Dinosaur Cove, one of the two major sites in southeast Australia, is where the authors worked with Earthwatch teams to reveal the special natural history of polar dinosaurs. Rich and Vickers-Rich summarize their pioneering work in this region in the recently published book, Dinosaurs of Darkness.
Half of the dinosaur taxa in southeastern Australia are made up of the family Hypsilophodontidae, small, terrestrial dinosaurs uncommon in other areas, which apparently flourished in the polar environment. Analysis of their bones suggests that they were constantly growing, and so were active throughout the year. A cast from inside the fossil skull of one of these dinosaurs shows that their brains had larger optic lobes than their lower latitude relatives. Their greater visual acuity may have helped them survive through the three-month-long polar night.
"On the basis of the shape of their brain, and the evidence from their bone structure that they did not hibernate but continued to be active all year long, hypsilophidontids seem to have been particularly well adapted to high latitudes," said Rich. "Consequently, it appears that polar conditions were particularly favorable to them."
Indeed, polar habitats may prove to have been nursery areas for terrestrial dinosaurs and other animals, as they have yielded many early records of forms that occur elsewhere later in the Cretaceous. "Polar Dinosaurs" demonstrates that the role of polar areas in the evolution of dinosaurs is a fertile area for further study.
The article by Rich and his colleagues was inspired by a talk he gave at the Natural History Museum of Los Angeles County on the same subject, arranged by Earthwatch Institute.
For more information, see: Polar Dinosaurs, by Thomas H. Rich, Patricia Vickers-Rich, and Roland A. Gangloff. Science, Volume 295, February 8, 2002, pp. 979-980.
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