|Frozen Siberian Cave Lions Cubs|
Over the last 24 days, we've seen lagerstätten preserved in many different ways, all of which have in some way helped tell the story of how climate change through the Cenozoic has affected life on land. Today, to close out the advent calendar, we're ending with specimens that share not a particular locality but rather a particular environment of preservation, one that only exists because of the cold climate of the Pleistocene. Original soft tissue - muscles, organs, skin, and hair - are not unheard of from the Pleistocene. Mummies have been preserved in dry caves across the globe: moas in New Zealand, thylacines in Australia, ground sloths in Patagonia and the Mojave Desert. Even more spectacular are those animals that have been frozen in the permafrost of the far reaches of the Northern Hemisphere. Permafrost is the frozen soil that underlies the tundra of Siberia and Alaska and, if any organism is buried in either region's sediments before being significantly scavenged or decomposed, it can become preserved in the subsurface ice. Melting during warmer periods or, more recently, mining brings these remains to light with surprising frequency. Because they consist of original organic material, these permafrost mummies do not qualify as fossils by everyone's definition. For those of us that do consider them to be a part of the fossil record, though, the Siberian and Alaskan permafrost constitute what has been referred to as "the ultimate lagerstätte." Frozen woolly rhinos have been unearthed, as have bison (see the University of Alaska's "Blue Babe" for a particularly well-known example), horses, and numerous other animals. Very recently, a discovery of frozen Siberian cave lion cubs made major waves, but historically (and as with many sites profiled in the last week) the real stars of the show are mammoths. In fact, a frozen woolly mammoth brought back to St. Petersburg at the end of the 18th Century was one of the first fossils of any type of organism to pique the interest of the general public. Today, permafrost mummies are sources of hugely valuable information about life in the subarctic regions of the world during the Pleistocene (they have also, unfortunately, become lightning rods for creationists, who have frequently made the claim that the specimens show evidence for rapid freezing, allegedly falsifying gradualist explanations for the history of Earth and its life - I need hardly remark that such evidence is, in fact, nonexistent). Organisms and ecosystems from the polar regions of the world are the first to feel the effects of climatic change, so the light that permafrost mummies can shed on how life has responded to periods of warming and cooling in the past could be invaluable for illuminating the future of modern subarctic organisms.
Visit: Permafrost is widespread (though increasingly rare) beneath the tundras of Alaska, Canada, and Russia. However, as a subsurface feature, it's not something easily observed. The best opportunity I know of for doing so is the Permafrost Tunnel Research Facility near Fairbanks. As a research site, it's not generally open to the public, but the Army Corps of Engineers does lead occasional tours.
Fossils: In the continental US, your best bet is the American Museum of Natural History, home to both a frozen mammoth and a frozen squirrel, nicely demonstrating that it's not just megafauna that were frozen. The University of Alaska Museum of the North has an especially important collection, including the aforementioned "Blue Babe." My lack of Russian language skills makes verification of this difficult, but the two museums that have historically housed permafrost mummies in that country are St. Petersburg's Zoological Museum and Moscow's Paleontological Museum.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Several! Enough, in fact, that I'll simply leave it to you all to search for one that suits your interests rather than linking to any in particular.
This post is part of my 2015 Paleontology Advent Calendar, a series of vignettes on lagerstätten - sites of exceptional fossil preservation - that document changes in climate and environments through the Cenozoic. You can see the other posts here.