Eocene lower vertebrates from Ellesmere Island, Canadian Arctic Archipelago

Lower vertebrates from the Early Eocene Eureka Sound Formation, Ellesmere Island, Canadian Arctic Archipelago, form a mixed aquatic—riparian—terrestrial assemblage similar to that of many North American Late Cretaceous and Paleogene continental deposits. Taxa include the bony fishes Amia and Lepisosteus, the salamander Piceoerpeton, anguid and varanid lizards and a boid snake. Turtles include two emylids, the tortoise Geochelone, and anosteirine, Trionyx s.s. and an unidentified turtle adapted for durophagy. The durophagous alligator Allognathosuchus is also present. The varanid, tortoise and alligator indicate an equable climate with winters that rarely suffered freezing temperatures. These animals (especially the varanid) have high temperature optima today. Such optima are more likely to have occurred seasonally, under present obliquity of the earth's axis, than with the low obliquity model that has been suggested by paleobotanical data. If so, these animals must have undergone periods of winter dormancy, unlike their living relatives. Zoogeographic affinities of the lower vertebrates are generally with North America although some of the taxa also occur in Palaeogene Europe; only the anosteirine turtle shows Asian affinities. Two of the taxa appear to have been endemic to the Arctic region, and the assemblages as a whole may have been part of a pan-Arctic fauna rather than resembling that of any northern continent in particular.