Eocene land vertebrates are rare, relatively recent, discoveries in the Canadian Arctic islands. The first were discovered in 1975 in Eocene-aged strata of the Eureka Sound Group, western Ellesmere Island, and reported by Dawson et al. (1976). Subsequent discoveries occurred in the 1980s in similar-aged strata on both Ellesmere and Axel Heiberg islands (Dawson, 1990; Dawson et al., 1993), bringing the tally of vertebrate families to over 30 (Marincovich et al., 1990; Dawson, 1990). The vertebrate fauna provides strong evidence for a mild, equable Arctic climate during the Eocene (Estes and Hutchison, 1980), corroborated by the paleoflora (Axelrod, 1984; Basinger, 1986, 1991). Supporting this interpretation, the isotopically-determined mean ocean surface temperature at 70°N was a mild 10-15°, a far cry from today's mean of −10° (Barron, 1987; Shackleton and Boersma, 1981; McKenna, 1980).