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Tertiary Paleoenvironment in Yukon, Canada.
Rhinocerotidae, Chrysemys pond turtle, Hesperotestudo tortoise, and Esox pike
in Eberle, Hutchison, Kennedy, et al., 2019.
DOI: 10.1206/3943.1
Illustration: Julius Csotonyi digitallibrary.amnh.org
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Abstract
Despite over a century of prospecting and field research, fossil vertebrates are exceedingly rare in Paleogene and Neogene rocks in northern Canada's Yukon Territory. Here, we describe the first records of probable Neogene vertebrate fossils from the territory, including tooth fragments of a rhinocerotid, a partial calcaneum of an artiodactyl, shell fragments of the pond turtle Chrysemys s.l. and tortoise Hesperotestudo, and a fragment of a palatine of Esox (pike). Although the tooth fragments cannot be identified solely by traditional paleontological means, we use tooth enamel microstructure, and primarily the presence of vertical Hunter-Schreger bands, to refer them to the Rhinocerotidae. As the only known record of the Rhinocerotidae in North America's western Arctic, the tooth fragments from the Wolf Creek site support the hypothesis that the clade dispersed between Asia and North America across Beringia. The fossils are consistent with a Miocene age for the Wolf Creek site that is inferred from radiometric dates of the Miles Canyon basalt flows in the vicinity of the fossil locality. Further, the tortoise and pond turtle fossils indicate a mild climate in the Yukon at the time, consistent with the vegetation reconstructions of others that indicate a warmer, wetter world in the Miocene than today.
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| FIGURE 9. A–B. Tangential section of YG514.12 (uncoated) viewed under a light microscope showing the bifurcating vertical HSB. A. Light source from top. B. Light source from bottom. C. SEM image of tangential section. D. Magnified bifurcation in region encompassed by white square in C, showing the steeply angled prisms comprising the HSB; transitional zones are the light-colored edges of the bifurcation. E. Magnified SEM image showing narrow transitional zone of horizontal prisms flanked by the steeply angled prisms that make up the vertical HSB. F. Vertical section of outer enamel showing the radial enamel wherein the prisms rise at a shallow angle toward the OES. Abbreviation: OES, outer enamel surface. |
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| an ancient relative of today's rhinoceroses splashing through a stream next to turtles and fish in the Yukon.
Illustration: Julius Csotonyi
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Jaelyn Eberle, J. Howard Hutchison, Kristen Kennedy, Wighart Von Koenigswald, Ross D.E. MacPhee and Grant Zazula. 2019. The First Tertiary Fossils of Mammals, Turtles, and Fish from Canada's Yukon. American Museum Novitates. (3943); 1-28. DOI: 10.1206/3943.1
Ancient rhinos roamed the Yukon phys.org/news/2019-10-ancient-rhinos-roamed-yukon.html via @physorg_com