Fossil fishes from the high Canadian Arctic: further palaeobiological evidence for extreme climatic warmth during the Late Cretaceous (Turonian–Coniacian)

Late Cretaceous (Turonian–Coniacian) sedimentary rocks of the high Canadian Arctic (Axel Heiberg Island) have yielded vertebrate fossils suggestive of extreme warmth. In addition to champsosaurs and turtles, the assemblage also contains fishes. Examination of larger fish elements, isolated teeth and scanning electron microscope studies of ganoin microstructure indicate the presence of lepisosteids, amiids, and teleosts. Interestingly, the only other known high-latitude occurrences of amiids and lepisosteids, fossil or recent, are from intervals of extreme warmth during the Tertiary. Examinations of the salinity and thermal tolerances of extant and fossil representatives of these taxa suggest that the Axel Heiberg fishes lived in a freshwater environment that was in communication with the marine realm. The comparison of both the herpetofauna and the ichthyofauna with other Cretaceous assemblages reveals similarities with those of lower latitude western North America, but disparities with an Alaskan assemblage thought to have been associated with cooler temperatures. These findings are consistent with mounting evidence for extreme Arctic warmth during Turonian–Coniacian times.