Wednesday 14 August 2019

Chasmaporthetes sp.: The first evidence of Hyenas within the Arctic Circle.

Hyenas first appeared in Eurasia in the Early Miocene, and rapidly diversified to become the most abundant predators in Eurasia, with more than 60 described species. At some point during the Plio-Pleistocene Hyenas reached North America, becoming common in the southern United States and Mexico during the Pleistocene, before disappearing there during the End Pleistocene Megafaunal Extinction. Hyenas are thought, like many other Mammal groups, to have reached the Americas via the Beringian Land Bridge, which connected Alaska to the Russian Far East during periods of low sealevel associated with the Pleistocene glaciations. However, to date this has been an entirely theoretical movement, with Hyena remains unknown from northern parts of the United States or Canada.

In a paper published in the journal Open Quaternary on 18 June 2019, Jack Tseng of the University at Buffalo, Grant Zazula of the Government of Yukon, and of Research and Collections at the Canadian Museum of Nature, and Lars Werdelin of the Swedish Museum of Natural History describe the first recorded Hyena specimens from the Pleistocene deposits of the Old Crow Basin, in the unglaciated region of northern Yukon Territory, Canada.

The material described comprises two isolated teeth, probably belonging to the species Chasmaporthetes ossiphragus, and certainly to a member of the genus Chasmaporthetes, from the CRH 11A locality, on a point bar near the downstream end of the basin. Over 50 000 reworked fossils from at least 80 vertebrate species have been recovered from point bars on the Old Crow River. The material is thought to be between 1.4 million and 12 000 years in age, but almost certainly more than 850 000 years old and probably closer to 1.4 million years old.

Hyena fossils from Old Crow, Yukon Territory, Canada. Chasmaporthetes cf. Chasmaporthetes ossifragus, CMN 24958, right p3: (A) lingual stereopair views, (B) labial stereopair views, (C) occlusal stereopair views. CMN 38053, left m1: (D) labial stereopair views, (E. lingual stereopair views, (F) occlusal stereopair views. Tseng et al. (2019).

The genus Chasmaporthetes has previously been recorded in buth Asia and North America, to its discovery in the Beringia region is not unexpected, though the most northerly American specimen previously discovered comes from Meade County in Kansas, more than 4000 km to the south, while the closest Asian specimens come from Shamar in Mongolia, roughly 6500 km away, with the distance between the two sites being over 10 000 km.

Fossil localities containing Chasmaporthetes. New material described in this study from Old Crow Basin (Locality 11A) is marked with a star. Dashed arrows indicate likely dispersal route evidenced by new fossils. Regions with more than one fossil locality are indicated with a quantity after the locality marker. Tseng et al. (2019).

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