Identifying fragmentary Mammal teeth from the Early Eocene of Ellesmere Island, Canada.
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Lower Eocene (Wasatchian-aged) strata of the Margaret Formation, Eureka Sound Group on Ellesmere Island, Nunavut preserve evidence of lush mixed conifer-broadleaf rainforests inhabited by Alligators, Turtles, Birds, and at least 25 Mammalian genera. First discovered in 1975 near the head of Strathcona Fiord, the vertebrate fossils in the Eureka Sound Group are few, fragmentary and weather-worn, which can make it challenging to identify them. By far the most abundant and diverse Vertebrate fossils have come from the Margaret Formation cropping out on the Matthew peninsula between Bay and Strathcona fiords. Nearly a century before the first discovery of Eocene Vertebrate fossils on Ellesmere, Eocene Arctic forests were first documented when Sergeant David Brainard, a survivor of the ill-fated Greely Expedition of 1881–1883, discovered petrified logs on northeastern Ellesmere Island. Among the best preserved, extensive, and photogenic of the Eocene Arctic fossil forests is the Strathcona Fiord Fossil Forest, which preserves permineralised in situ tree stumps protruding from a prominent coal seam. The tree stumps are large, with diameters ranging from 40 cm to over a meter, and closely spaced, indicating a dense forest comparable to today’s Cypress swamps in the southern United States. Eocene Arctic palaeotemperature estimates using multiple proxies suggest a mean annual temperature of 5–17˚C, with winters above freezing and summer temperatures above 20˚C. Further, the Eocene Arctic rainforests had high mean annual precipitation and humidity, comparable with today’s temperate rainforests along the North American west coast.