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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Understanding the demise of the last Mammoths of St Paul Island.

Mammoths, Mammuthus spp., disappeared from the mainlands of Eurasia and North America around the end of the last Pleistocene glaciation, between 14 000 and 13 200 years ago, with some populations having possibly persisted as late as 10 500 years ago. However populations of Woolly Mammoths, Mammuthus primigenius, are known to have survived on several Beringian islands long after the end of the Pleistocene, with the last populations having survived on Wrangel Island (north of Siberia) till about 4020 years ago and St. Paul Island (in the Pribilof Islands of the Bering Sea) till around 5600 years ago. The demise of the Mammoths of Wrangel Island is known to have occurred around the time the first Humans arrived on the island, suggesting strongly that they may have become extinct directly due to Human activity. However the first Humans to reach St. Paul Island thought to have arived in the late eighteenth century, long after the demise of the island's last Mammoths, suggesting that another cause must have been responsible for there demise.

In a paper published in the Proceedings of the National Academy of Sciences of the United States of America on 1 August 2016 a team of scientists led by Russell Graham of the Department of Geosciences at The Pennsylvania State University describe the results of a study into the demise of the last Mammoths of St Paul Island.

St Paul Island is thought to have been cut off from the Bering Land Bridge between 14 700 and 13 500 years ago, and shrunk rapdily in size until about 9000 years ago, then more slowly untill about 6000 years ago, when it reached approximately its current size.

The previous last recorded date for Mammoths on St Paul Island was about 6480 years ago, but such dates are not generally thought to represent the last actual date a species was present. Graham et al. carried out radiocarbon dating of collagen from 14 newly discovered Mammoth remains from the island, obtaining a latest date of 5530 years ago, ~about 950 years after the previous last date for Mammoths on St Paul Island, but still ~1500 years before the last known date for Mammoths on Wrangel Island.

Map of current continents (dark gray) and the past position of the Bering Land Bridge (light gray) with red boxes indicating Wrangel Island (Upper) and St. Paul Island (Lower). Graham et al. (2016).

Graham et al. then examined a series of sediment cores from Lake Hill, a freshwater lake near the center of the island, and the largest and deepest body of water on the island at about 1.3 m. These were then examined for four different climatic proxies across the period when the Mammoths disappeared. These were the spores of three coprophilous Fungi (species that specialize in growing on animal dung) Sporormiella, Sordaria, and Podospora and the presence and nature of sedimentary DNA. The general environement was reconstructed across this period using a variety of proxies including Cladocerans, Diatoms, pollen, plant macroremains, and stable isotopes, and dated using radiocarbon dates from the plant macroremains and tephrochronology (isotope dates from volcanic ash layers).

Mammoth DNA was present in soil samples till about 5650 years ago, while the coprophilous Fungi Sporormiella and Sordaria disappeared 5680 and 5650 years ago respectively (Podospora disappeared much earlier), supporting the idea that the last Mammoths lived on the island about five and a half milenia ago. 

This date coencides with a marked drying of the environment on the island, as indicated by the environmental proxies. Species of Cladocerans and Diatoms associated with a planktonic lifestyle in clear, deep, lake waters disappear, and are replaced by specues associated with shallow, turbid (muddy) waters. 

This timing also coencides with a period of increased climatic instability recorded in other parts of the Aluetian Islands and Alaska, which would be consistent with reduced rainfall on the island lowering the availability of fresh water. Modern Indian and African Elephants consume between 70 and 200 litres of water per day, and Mammoths are likely to have had similar requirements, suggesting that any such draught could have hit a small island population very hard. Under such circumstances the Mammoths may have been forced to crowd around a few greatly reduced water sources, which would have led to further environmental degredation, causing increased erosion around the pools and degrading the water quality.

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X-ray Computed Tomography studies of two Woolly Mammoth calves from Russia.            The Woolly Mammoth, Mammuthus primigenius, is thought to have diverged from the earlier Steppe Mammoth Mammuthus trogontherii in northeast...

The Dwarf Pachyderms of Crete, Mammoths or Straight-Tusked Elephants?                  Fossil Dwarf Elephants are known from a number of small islands around the world; this is not altogether surprising, dwarfism is common in populations of animals cut of on small islands (as is giantism). Animals in such environments often need to adapt to...

What Nitrogen tells us about the diet of Mammoths.                                             Nitrogen has two stable isotopes, Nitrogen-14 (¹⁴N) and Nitrogen-15 (¹⁵N), which have different atomic weights, but identical chemical properties, and can be incorporated into identical compounds by...

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