ABSTRACT

The Gunnison River of western Colorado is famous as a sport fishing destination for those interested in fly-fishing for various kinds of trout. The canyon, which can be thousands of feet deep, exposes some of the oldest rocks in North America, and in some places along the canyon it is deeper than it is wide. The Arctic bonebeds that produced the thousands of dinosaur bones that form the basis of much of what people know about Arctic dinosaurs were formed under unique conditions and regional climate. The ancient Arctic coastal plain was influenced by seasonally varying hydrologic processes, water levels, and by what appear to have been episodic floods. Arctic dinosaurs may have effectively starved during the winter and reproduced during the short summer. Some dinosaurs were and are endotherms, but perhaps some were instead more like reptiles in their physiology— the large-bodied extreme of an ectothermic life history phenomenon.