25 December 2015

Fossils 'Neath the Tree

video
Of course, one of the joys of any advent calendar is the payoff at the end, so here's my gift to you: lots and lots of lagerstätten set to Tchaikovsky.  Note that I only used my photos, so not every site I highlighted is included and there's a strong emphasis on Neogene mammals.  Happy Holidays!

24 December 2015

24. Frozen Mummies of the Far North

Frozen Siberian Cave Lions Cubs
National Geographic
Location: Siberia, Russia & Alaska, USA
Age: Pleistocene

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.

23 December 2015

23. Tanque Loma

Reconstruction & Skeleton of Eremotherium at the Museo Paleontologico Megaterio
University of California Museum of Paleontology
Location: Santa Elena, Ecuador
Age: Pleistocene (24,000-17,000 years ago)

While the North American megafauna consisted of animals such as mammoths and mastodons, horses and tapirs, bears and dogs, and bison and camels - all of which would have been, to varying degrees, familiar in Pleistocene Asia, Europe, or Africa - the megafauna of South America had very different roots.  Until late in the Cenozoic, it had been the most isolated of island continents, populated by birds and mammals that had evolved there and that had no close relatives anywhere else in the world (as well as, bizarrely, monkeys and rodents that apparently rafted to the continent on storm-tossed vegetation).  However, as temperatures cooled and sea levels dropped (and, even more importantly, as the volcanic Isthmus of Panama began to form late in the Miocene), a land bridge formed that would connect the Americas.  Over millions of years and in several waves, animals migrated across Central America in both directions.  The effect this had on North America is attested to by the success of now-extinct ground sloths, glyptodonts, and "terror birds," as well as by the continued prosperity of armadillos, opossums, and porcupines, all taxa with origins south of Panama.  Several South American sites document the effect that the so-called American biotic interchange on native ecosystems.  One of the most-recently described is a site that has drawn comparisons to Rancho La Brea: the asphalt beds of Tanque Loma in coastal Ecuador.  This site contains remains of North American migrants: mastodonts, horses, and deer.  Contrary to the traditional narrative that northern invaders outcompeted their austral counterparts, Tanque Loma also preserves a rich array of South American taxa, notably giant ground sloths, the most iconic of the native megafauna.  Among these, the huge Eremotherium is particularly abundant, leading to the suggestion that it may have been a gregarious animal that congregated in the area.  Unlike Rancho La Brea, though, they were not trapped there, or at least not by asphalt.  Unusually, the asphalt at Tanque Loma seems to have infiltrated the local sediments well after the fossils were deposited, helping to preserve the bone bed, but not to form it.

Visit: I'm not certain what the preservation status of this site is, but I'm fairly certain it is not open for visitation.
Fossils: The Museo Paleontologico Megaterio on the campus of the Universidad Estatal Península de Santa Elena was constructed specifically to house specimens from Tanque Loma.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: No, probably in large part because of how recently described the site is, but if you want more information on it you can check out Emily Lindsey's descriptive paper.

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.

22 December 2015

22. The Mammoth Site

The Mammoth Site
Location: South Dakota, USA
Age: Pleistocene (26,000 years ago)

The Waco Mammoth Site, profiled a couple of days ago, is a moment (or, to be precise, three moments) frozen in time.  Catastrophic events that entomb numerous animals simultaneously, as happened at Ashfall as well as at Waco, are one way to get a konzentrat lagerstätte.  Rancho La Brea illustrates the other way to generate a bone bed: have some kind of natural trap in which specimens build up over time.  This method is also nicely illustrated by a second mammoth-rich locality a few states north of Waco.  On the southern edge of the Black Hills, a sinkhole opened up roughly 26,000 years ago.  A lake formed in this sinkhole that served as a home to invertebrates and fish and as a pitfall trap to terrestrial organisms.  While these range from rodents to bears (including some of the best remains of the giant short-faced bear Arctodus ever found outside of Rancho La Brea), the majority of the animals preserved here are mammoths.  Delightfully to those of us who enjoy exposing the "everything's bigger in Texas" mantra for the lie it is, more than twice as many individuals have been uncovered from the South Dakota site, representing both Columbian and woolly mammoths.  As has been clearly established by the last couple of posts, Columbian mammoths are widespread across North America, but the presence of their cold-adapted relative in the Black Hills illustrates an important trend in Pleistocene climate.  While the "global hothouse" of the Eocene is a bit of an oversimplification (see the earlier posts on the Okanogan and Florissant), it is true that the difference in climate between the poles and the equator was smaller early in the Cenozoic than it is today.  However, the presence of a species usually associated with tundra and other cold environments - and its absence from a site less than a thousand miles to the south - demonstrates that the strong latitudinal gradients associated with temperature today were solidly in place by the Pleistocene (though with the caveat that, because it sits at a relatively high altitude, the Mammoth Site is not a perfect analog for lower-lying localities at the same latitude).  This increase in the difference in climate between more polar and more equatorial ecosystems may seem somewhat trivial, but it's long been suggested that this difference plays a major role in driving several ecological and evolutionary trends.  Not only was climate in the Pleistocene abnormally cold and variable, then, but life on land was affected by huge climatic extremes even within the confines of a single continent.  Lagerstätte such as the Mammoth Site and Rancho La Brea show how North American organisms and ecosystems responded to this new climatic regime, but things looked quite different one continent to the south.

Visit: If you live in the US, at some point in your life you'll make the requisite trip to Mt. Rushmore.  Spend as little time as possible there and head south to the sites that really should be headlining your Black Hills itinerary: Custer State Park, Wind Cave, and Hot Springs, where the Mammoth Site has been developed into an excellent on-site museum.
Fossils: Most of the mammoths from the Mammoth Site remain in situ, and anything that's been excavated has remained on-site at the museum.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: There is, published by the museum in Hot Springs, whose web site seems to be temporarily down, meaning I can't link to it.

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.

21 December 2015

21. Rancho La Brea

Dire Wolf Skulls
Page Museum
Location: California, USA
Age: Pleistocene-Holocene (55,000 years ago-Recent)

Many Cenozoic lagerstätten have produced more fossils (Fossil Lake, for example) and many have higher quality of preservation (such as Messel), but none is as widely known as the "tar pits" of Rancho La Brea.  Part of the reason for this fame is likely the location of the site, on Wilshire Boulevard in the middle of Los Angeles.  Part of it is due to the unusual method of preservation, in which animals were trapped and eventually buried in asphalt seeps.  The bulk of La Brea's fame, though, is due to the fossils uncovered there, which include megafaunal mainstays - mammoths, sloths, camels, and horses - as well as rarer large mammals, such as tapirs, and a wide variety of small-bodied animals.  The most spectacular fossils from La Brea are its predators, which are found in huge numbers (in the thousands, in the case of especially common species).  Coyotes (originally described as their own species, Canis orcutti, sadly no longer recognized as distinct from the living C. latrans) and dire wolves are particularly abundant, as is Smilodon, the saber-toothed cat that has such wide appeal that it was designated California's state fossil.  Other big predators that show up at Rancho La Brea include the extinct American lion Panthera atrox, the scimitar-toothed cat Homotherium, and the giant short-faced bear Arctodus, as well as still-living predators such as cougars, timber wolves, and black bears.  It's not just mammalian predators that are abundant at the site: a wide variety of raptors have been found here in larger numbers that anywhere else, including familiar taxa such as hawks, eagles, and condors, but also the extinct Teratornis (which besides being impressive in and of itself, has a fantastic name that translates as "Monster Bird").  Why so many predators?  It's long been hypothesized that prey animals trapped in asphalt would have served as lures for carnivorous animals, many of which would have then become trapped themselves, providing ever more carrion to be had.  Recent research (including, at the risk of indulging in self-promotion, some of my own) has supported this hypothesis, further suggesting that the abundance of large and/or social predators at La Brea implies that animals particularly adept at defending carcasses from other scavengers were frequently preserved at the site.  This is just one example of how Rancho La Brea fossils have been used to reconstruct the biology of Pleistocene organisms.  Other long-standing areas of study have been whether or not Smilodon was social (a highly unusual trait among living cats) and, more relevant to the theme I've been following all month, how climate change through the Pleistocene and Holocene have affected the La Brea biota.

Visit: The LA area is home to several of the world's great museums, and even among that distinguished milieu, the George C. Page Museum of La Brea Discoveries in Hancock Park is a standout.  Besides the museum itself, several asphalt pools, excavation sites, and megafaunal statues are on view in the park.
Fossils: Almost every major natural history museum has a few Rancho La Brea specimens.  The Page Museum is the best spot to see them in the LA area, but several specimens are on display at its parent museum, the LA County Museum, as well.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: There is!

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.

20 December 2015

20. Waco Mammoth

Columbian Mammoths from the Waco Mammoth Site
Larry D. Moore, Wikimedia
Location: Texas, USA
Age: Pleistocene (68,000-53,000 years ago)

Snowmass is known for its mastodons, proboscideans - members of the same order of mammals as elephants - that were early stars of the North American fossil record.  In time, though, their status in the popular imagination as iconic megafauna would be usurped by another type of proboscidean: mammoths.  Mammoths are much closer relatives of elephants (they are, in fact, more closely related to Asian elephants than are African elephants) and while the most famous of them is Mammuthus primigenius (the woolly mammoth), the most widespread species in North America is the Columbian mammoth, Mammuthus columbi.  They are well-represented at several sites across the continent and have figured prominently in the debate over whether human activity or climate change played a larger role in the extinction of megafauna at the close of the Pleistocene.  In at least one case, though, the death of several mammoths can be clearly attributed to natural causes.  In what is now Waco, Texas, a flash flood 68,000 years ago killed and buried a herd of Columbian mammoths, making the site, like Ashfall, a snapshot of a moment in time.  Unusually, many of the individuals at the Waco Mammoth Site are juveniles, leading to the suggestion that the group killed in the flood was a nursery herd.  Other layers at the site preserve younger, less fatal floods, that preserved more mammoths and, among other things, remains of another icon of the Ice Ages: the saber-toothed cat Smilodon.  As with all mammalian predators, Smilodon tends to be much less common than its prey at most localities, and were this true everywhere, it might remain a somewhat enigmatic animal.  Fortunately, just as the Waco Mammoth Site preserves huge concentrations of herbivores, other sites have done the same for the animals that preyed upon them.

Visit: This July, President Obama designated the Waco Mammoth Site a national monument, preserving the locality - and guaranteeing its visitability - in perpetuity.
Fossils: To the best of my knowledge, all of the fossils from Waco remain on-site.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Not that I'm aware of.

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.

19 December 2015

19. Snowmass

Bison latifrons skull at Snowmass
Denver Museum of Nature & Science
Location: Colorado, USA
Age: Pleistocene (140,000-55,000 years ago)

While diprotodonts and kangaroos were getting trapped in the caves of Naracoorte, an entirely different group of megafauna existed in North America.  Perhaps our best window into what this fauna looked like before the arrival of humans is provided, unusually, by a high-elevation site west of Denver.  Skiers are likely familiar with Snowmass, one of the many resort towns that dot the Colorado Rockies, but since 2010 it has become a familiar place to paleontologists as well.  While expanding a reservoir in town, a bulldozer operator uncovered the remains of a much older, natural body of water: a lake that had entombed the remains of numerous Pleistocene organisms.  The nickname of the site, Snowmastodon, is due to the large numbers of American mastodon (Mammut americanum) found there.  Also present are other mainstays of the continent's megafauna, notably the mastodonts' distant relative the Columbian mammoth (Mammuthus columbi), the ground sloth Megalonyx jeffersoni, the long-horned Bison latifrons, as well as camels, horses, and deer.  Snowmass is more than just a megafaunal bone bed, though: also recovered from the site have been small animals such as reptiles, amphibians, rodents, and fish, as well as plant and pollen fossils.  These last have been especially important in reconstructing environmental responses to climate change through time and are a nice illustration of how variable the response of ecosystems to change can be; during one cooling event, for example, Snowmass seems to have stayed relatively warm, while during another its decrease in temperature was greater than the global average.  Unusual among North American megafauna sites, the Snowmastodon fossils were deposited entirely prior to the arrival of humans to the continent, making it an ideal study site for those interested in the changes to an ecosystem brought about by climate and other natural factors.

Visit: The town of Snowmass operates an Ice Age Discovery Center focusing on the site.
Fossils: The Denver Museum of Nature & Science, an excellent museum and a long-time personal favorite, is the repository for all Snowmass material.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Not for adults, but Kirk Johnson, one of our greatest paleontological ambassadors, has written a book about the site for kids.

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.

18 December 2015

18. Naracoorte

Thylacoleo, the "marsupial lion," at Naracoorte
Wikimedia
Location: South Australia
Age: Pleistocene-Holocene (530,000 years ago - Recent)

And so we arrive in the Pleistocene, the "Ice Age" of popular imagination and the culmination of the gradual cooling of the Miocene and Pliocene.  While the planet's temperature was lower on average than it had been since well before the evolution of the dinosaurs, Earth was not covered entirely in ice and tundra.  Periods of glacial advance were followed by warmer periods, this cycle driven largely by alterations in orbital dynamics.  Many parts of the globe remained glacier-free even during colder intervals, and prominent among these areas was Australia.  While never glaciated, the continent's environments were radically changed by climatic cooling and drying, a process that we have already seen illustrated in the north at Riversleigh.  In the far south, the Pleistocene landscape was dominated by eucalyptus woodlands, an environment still familiar to modern visitors to the region.  Unlike today, these woodlands were populated by Australia's endemic megafauna, a term used to describe the large mammal (and in Australia's case, reptile and bird) faunas of each continent during the Pleistocene.  At Naracoorte in what is now South Australia, a series of caves acted as natural pitfall traps into which animals occasionally fell, a process that over several thousand years led to meters-thick megafauna bone beds (this style of preservation is a recurring theme in Pleistocene lagerstätten, another excellent example being Wyoming's Natural Trap Cave).  In fact, animals of all sizes are preserved at Naracoorte, including some personal favorites, the shrew- to rat-sized carnivorous dasyurid marsupials.  However, the stars of the show are the impressive number of organisms to which the adjective "giant" can be appended: the giant snake Wonambi, the giant lizard Megalania, the giant bird Genyornis, the giant kangaroo Procoptodon, the giant-by-any-standards Diprotodon, and so on.  As with megafauna across the globe, there are several Naracoorte animals that have no close living relatives and, in this case, defy comparisons to anything alive today, the prime examples being the bizarre (even by Australian standards) Palorchestes and Thylacoleo.  Perhaps the most widely asked question about megafauna on any continent is why so few of them are around today.  Was it a result of changes in the ever-cycling Pleistocene climate or of the spread of our own species?  Spanning as it does the whole of human occupation of Australia, Naracoorte is one place that lends itself to addressing this question, but it is in North America that the debate has reached its most intense.

Visit: Naracoorte Caves National Park south of Adelaide, part of the same World Heritage Site as Riversleigh, allows visits to some of the fossil-bearing caves.
Fossils: The official repository for Naracoorte material is the South Australian Museum in Adelaide, though I believe a fair amount of material has made its way to the Australian Museum in Sydney as well.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Not that I'm aware of.

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.

17 December 2015

17. Hominid Sites of Lake Turkana

Nariokotome Boy
National Museum of Kenya
Location: Marsabit & Turkana, Kenya
Formation: Several, most notably the Koobi Fora Formation
Age: Pliocene-Pleistocene (4-2 Ma)

If the story of climate change through the Cenozoic is one of cooling and drying, the principle drama that has been played out in terms of environment is the interplay between forests and grasslands.  Both because of the number of lagerstätten there and the amount of research that has been focused them, the stage on which this drama is often set is North America.  However, places like the steppes of Central Asia and the pampas of South America tell much the same story.  So too do the savannahs of Africa, and these have been the subject of a great deal of study because they factor prominently in our own evolutionary story.  Like much of the world, Africa saw its forests give way to open environments during the Miocene, while at the same the continent began to fracture along the Great Rift Valley as the Horn of Africa began to move eastward.  The wide array of scattered environments, it has been argued, were the impetus for our earliest ancestors to leave the trees and begin walking upright (though, like almost every hypothesis in the subdiscipline of paleoenthropology, this is by no means universally accepted).  Regardless of what originally drove a particular group of apes to evolve an erect posture, by the latest Miocene and into the following epochs, the Pliocene and Pleistocene, hominins - the subfamily of Primates to which we belong - had begun to diversify into a variety of forms.  Sites along the Kenyan shorelines of Lake Turkana preserve an especially high concentration of hominin fossils, from the enigmatic Kenyanthropus, to Australopithecus (best known as the genus to which Lucy belonged, and also well known from sites in Ethiopia and South Africa), to Paranthropus (easily the most bizarre branch of the hominin tree, with enormous and robust skulls that isotopic analyses have suggested were adapted to a diet of bamboo), to members of our own genus, Homo.  The most spectacular Turkana fossil from this last category is the so-called Nariokotome Boy, a specimen assigned variously to H. erectus and H. ergaster.  The nearly complete skeleton, found on the western shore of the lake, is not only spectacular in and of itself, but is one of the best sources of information available about our own branch of the hominin tree.  The oldest rocks along Lake Turkana date to a time when the entirety of human evolution had taken place in Africa.  By the time Nariokotome Boy was alive, though, members of our genus had begun to spread across the rest of the world, where they would encounter Pleistocene ecosystems that would form the basis of some of the Cenozoic's most stunning lagerstätten and in which they would, in many cases, figure prominently.

Visit: A series of national parks surround Lake Turkana, many designated as World Heritage Sites.
Fossils: Fossil material from throughout the country is reposited in Nairobi's National Museum, but having never been, I can't vouch for how much Turkana material is on display.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: No, though several books focusing on human evolution are available.

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.

16 December 2015

16. Gray Fossil Site

Rhinos, alligators, and tapirs from the Gray Site
Phil Fraley Productions
Location: Tennessee, USA
Formation: Sediment fill in the Knox Group
Age: Miocene (7-5 Ma)

By the end of the Miocene, grasslands had expanded across the interiors of most continents, but that is not to say that forests went extinct.  In places where temperature and precipitation remained favorable, forests of various kinds continued to flourish even as global climate cooled and dried.  The Appalachians were one such area, and at the end of the Miocene they were blanketed in woods of oak, hickory, and pine similar in many ways to those of the southern end of the mountain range today.  East Tennessee sits atop carbonate rocks that can be dissolved by water, leading in places to the collapse of overlying sediments to form sinkholes.  One such sinkhole in eastern Tennessee that existed in the closing days of the Miocene accumulated the remains of plants and animals from the area that would eventually become one of the richest vertebrate fossil-bearing sites in eastern North America.  Because it represents a forest from an interval with a fossil record dominated by grasslands, the Gray Fossil Site has yielded many animals not commonly seen elsewhere.  Perhaps the most interesting of these are animals that migrated to North America from elsewhere as cooling temperatures, lowering sea levels, and the movement of tectonic plates facilitated the movement of species across the globe.  North America and Asia were connected many times over the course of the Cenozoic, and some Asian immigrants found at the Gray Site, such as elephant-like gomphotheres and cats (including some of the saber-toothed variety), had arrived on the continent in the mid-Miocene.  Others, such as bears and, bizarrely, red pandas, were much more recent arrivals.  Perhaps most significant of all, though, were giant ground sloths, the earliest and among the most successful of migrants from South America, which until the end of the Miocene had been comparable to Australia in its isolation from the rest of the world.  There are also plenty of North American natives at the Gray Site, the most common of which were tapirs (which, though they are extinct on the continent today, have a fossil record here dating back to the Eocene).  The dwarf species Tapirus polkensis has been found in such numbers, and in such good states of preservation, that it's been the focus of population ecology analyses, an area of study that usually cannot be applied to fossil vertebrates.

Visit: East Tennessee State University in Johnson City owns the Gray Site and operates a museum there.
Fossils: As opposed to many of the lagerstätten featured this month, fossils of which are often scattered through several collections, pretty much everything from the Gray Site has wound up in the ETSU collections.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: There is!

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.

15 December 2015

15. Ashfall

The Ashfall Bone Bed
Location: Nebraska, USA
Formation: Ash Hollow Formation
Age: Miocene (12 Ma)

We've seen several lagerstätten that preserve gorgeous fossils over the course of the month, but most of these are from sites in which remains of organisms accumulated over the course of long periods of time.  Moments of time are only rarely preserved in the fossil record, and Ashfall is among the very few sites to do so.  Twelve million years ago, the Great Plains had begun to take on their modern appearance, while to the west, what would become the Boise area sat atop the volcano that today fuels the geysers and hot springs of Yellowstone.  Eruptions of this titanic volcano produced immense clouds of ash, one of which settled onto a watering hole in northeast Nebraska, starving and suffocating the local wildlife and creating Ashfall.  Small animals died first, probably within hours, as shown by their abundance at the bottom of the ash layer.  Larger animals took up to a few weeks to die, and are consequently more common at the top of the bone bed.  The resulting deposit is not only full of complete skeletons, even of such fragile animals as birds and amphibians, but provides a snapshot of life on the nascent Great Plains that provides endless opportunities for research.  Interested in evolution and anatomy?  Nowhere will you find as many complete and articulated skeletons of everything from camels to snakes as at Ashfall.  Interested in the behavior of extinct mammals?  A whole herd of rhinos is entombed, providing even better evidence than the Agate bone beds of the evolution of herding behavior in plains animals.  Development?  Some taxa, particularly the horse Pseudhipparion, are represented by everything from newborns to full-grown adults.  Paleoecology?  An entire ecosystem preserved in the blink of a geological eye is present here.  Paleopathology?  Larger animals show signs of abnormal bone growth associated with high rates of volcanic particulate in the atmosphere.  Taphonomy?  Not only was the speed of burial unusually fast, but preservation in a layer of volcanic ash is also rare in the fossil record.  In short, Ashfall is more than simply a treasure trove of fossils: more than any other lagerstätte featured this month, it is a frozen moment in time and a font of information about the evolution of life on the Great Plains.

Visit: The "Rhino Barn" at Ashfall Fossil Beds State Historical Park should be at or near the top of everyone's paleontology life list.  It's a bit out of the way from pretty much anywhere, but well worth the detour.
Fossils: Most of the really spectacular fossils from Ashfall remain in situ, but the University of Nebraska State Museum in Lincoln houses and displays specimens excavated from the site.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: There is, and it's hot off the presses!  Information about it is available in the link to the State Historical Park above.

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.

14 December 2015

14. The Barstow Arthropods

The fly Dasyhelea, preserved in three dimension in the Barstow Formation
Farrall Smith
Location: California, USA
Formation: Barstow Formation
Age: Miocene (16-13 Ma)

The Mid-Miocene Climatic Optimum falls in the midst of a subdivision of the Miocene known in North America as the Barstovian Land Mammal Age, named for Barstow, California.  While the city is famous today as the midpoint between Los Angeles and Las Vegas and for being the very worst the Golden State has to offer, it has considerable fame among paleontologists.  This is primarily due to its mammal fauna, represented both by skeletal material and, more unusually, by trackways.  As productive as the  mammal-bearing units of the Barstow Formation are, though, it is the remains of insects that qualify certain units as lagerstätten.  We've seen a few localities with well-preserved insects, but in most cases (Riverlseigh being the one big exception), these are preserved as flattened remains or as trace fossils (chewed leaves, social insect nests, and the like).  At Barstow, the exoskeletons of insects and other arthropods were replaced by silica-rich minerals, strengthening them and allowing animals to be preserved in three dimensions.  The most abundant of these fossils are adults and larvae of salt-tolerant insects (especially beetles and flies) and fairy shrimp, which are neither insects nor shrimp, but crustaceans that specialize in living in ephemeral desert ponds.  The species preserved in the Barstow insect beds show that, while Nebraska may have been covered in grasslands and Idaho was home to deciduous forests in the mid-Miocene, southern California was a much drier place (not a huge surprise, given Barstow's modern location in the midst of the Mojave Desert).  More than that, the composition of the arthropod fauna changes between beds, showing that the landscape got ever more arid as time passed.  This likely was driven local climatic changes related to the uplift of the land and the shallowing of the lake in which the fossils were preserved, but also reflects a global trend.  While we tend to think of climate change solely in terms of temperature, other variables fluctuate through time as well.  As the MMCO ended and temperatures began their slow, steady decline, most areas of the world also saw less precipitation.  This increase in aridity is very nicely illustrated by the Barstow arthropods and would, among other things, play a major role in the increased global spread of grasslands and animals adapted to a life on the open range.

Visit: The Barstow insect localities are located on BLM land, but there are no visitor facilities associated with them that I'm aware of.
Fossils: Barstow mammal fossils stars of the show at many Southern California museums, such as the LA County Museum, the Raymond Alf Museum, and the San Bernardino County Museum.  To the best of my knowledge, the insect fossils are not exhibited anywhere.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Nope.

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.

13 December 2015

13. Clarkia

Chestnuts from Clarkia
William C. Rember, University of Idaho
Location: Idaho, USA
Formation: Clarkia Formation
Age: Miocene (15 Ma)

While the Great Plains began to take on a modern appearance at least as early as the beginning of the Miocene, the response of vegetation to changing climate was somewhat more complex elsewhere.  Around 16 million years ago, global climate warmed once more in an event known as the Mid-Miocene Climatic Optimum (or MMCO), after which it would steadily cool, culminating millions of years later in the Pleistocene Ice Ages.  During this final burst of warmth before the protracted cool of the Late Miocene and beyond, parts of the world saw forests reclaim land that had previously been dominated by open woodlands, savannahs, and grasslands.  This was certainly the case in the Northwest, where several floras show a flourishing of trees, with none doing so more spectacularly than the Clarkia Flora of northern Idaho.  The fossils uncovered from the site - including Metasequoia, beeches, maples, and walnuts - indicate a climate comparable to that of the older Bridge Creek Flora and to the modern Southeast US and temperate Asia.  While the plants of Clarkia may tell a familiar taxonomic and environmental story, their quality of preservation is unique.  Fossils in the lower units of the site were entombed in an anoxic environment, and this lack of oxygen has preserved not just details of their anatomy, but actual organic tissue.  This means that, before being exposed to oxygen, many of the leaves retain their original colors.  More importantly, molecular biology and paleontology generally exist in two very separate worlds, but Clarkia fossils allow biochemical and genetic studies that would be impossible at other localities.  Being able to study paleobiology on both a micro- and macroscopic scale is rare in general, and almost unheard of for fossils as old as 15 million years, making Clarkia stand out even in a region known for its fossil floras.

Visit: The site used to be open to private collecting for a fee, but all recent searches for it lead back to the Fossil Bowl dirt bike trackway in Clarkia.  I confess to a sense of deep foreboding about the condition of this internationally important locality today.
Fossils: Information about the location of Clarkia fossils is as ephemeral as information about the site itself.  The original collections were stored in the UI College of Mines Museum.  The College of Mines no longer exists, and the department it was subsumed into provides no hint as to where the fossils are currently stored.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Given the inexplicable obscurity into which the site seems to have sunk, it probably shouldn't surprise you that there isn't.

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.

12 December 2015

12. The Bone Beds of Agate

The entelodont Daeodon scavenging the corpse of the chalicothere Moropus
Agate Fossil Beds National Monument
Location: Nebraska, USA
Formation: Harrison & Anderson Ranch Formations
Age: Miocene (23-19 Ma)

While global temperature rebounded somewhat at the end of the Oligocene and at the beginning of the following Miocene Epoch, the global jungles and forests of the Eocene were gone.  In place of the trees that had blanketed landscapes from Scandinavia to the Australia, grass was beginning to take over.  Grasslands were a novelty at the beginning of the Eocene, increasingly common by the end of the Miocene, and are among the most widespread biomes on Earth today.  They are affected by climate, tending to grow in cooler, drier environments than forests, but they also play a major role in shaping climate as well as the organisms that occupy them.  One of the best places to observe these effects is in a place still known for its plains today: the panhandle of Nebraska.  Erosion by the Niobrara River has exposed a number of mammal fossil-bearing localities in the area, including some konzentrat-lagerstätten in the form of spectacularly productive bone beds.  Animals found here include relatives of familiar plains-dwellers such as horses, camels, and rhinos, as well as extinct taxa such as pig-like (but probably predatory) entelodonts, bear-dogs, and, strangest of all, chalicotheres (which I can only describe as horse-rhino-panda hybrids).  Many of these animals show what clearly seem to be adaptations to living in grasslands: long legs reflecting greater running ability, larger size, and defensive structures, all necessitated by the absence of trees in which to hide or from which to ambush prey.  Even among small mammals, adaptations to this new ecosystem are apparent, most notably in the beaver Paleocastor which, millions of years before its relatives became aquatic, was tunneling beneath the Nebraska plains, leaving behind the burrows known to early fossil hunters as "Devil's Corkscrews."  Other characteristics of Agate mammals may or may not reflect the pressures of grassland life.  The higher crowned teeth that were beginning to evolve in taxa such as camels and horses were long explained as adaptations to a diet of abrasive grass, but many recent studies have suggested that the connection between tooth height and grass abundance is not as close as once thought.  The bone beds themselves were long interpreted as evidence of herd behavior and living in large groups would certainly be useful in an open landscape, as it provides safety in numbers for herbivores and allows pack hunting in carnivores.  In some cases, the bone beds may indeed represent the death of several members of a herd around a watering hole during a drought, but it's also possible that the bones accumulated over a long period of time or were concentrated in particular locations by rivers.

Visit: Agate Fossil Beds National Monument, south of Harrison, preserves the most important historic bone beds as well as several Paleocastor burrows.
Fossils: The national monument visitor center has some nice fossil displays, but much of the best Agate material can be seen at the American Museum of Natural History, the Carnegie Museum, and the University of Nebraska State Museum, though there's hardly a major museum in the country without a specimen or two from the area.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: The Park Service publishes a nice, if somewhat dated, overview of the science and history of Agate.

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.

11 December 2015

11. Caribbean Amber

Ichneumonid wasp in Dominican amber
George Poinar, Jr., Wikimedia
Location: Dominican Republic &Haiti
Formation: Numerous
Age: Oligocene (25 Ma)

Many of the fossils presented here this month are figurative gems, but a few sites literally preserve fossils within gemstones.  As any fan of trivia will tell you, there are two gems created by organisms: pearls and amber.  As hardened tree resin, amber is itself a fossil, but the fossils most often associated with amber are the remains of organisms entombed within.  These can range in size and taxonomy from pollen grains to vertebrates, but most famously includes insects, which are preserved in resin relatively frequently.  Two region of the world are especially well-known for their amber lagerstätten: the Baltic Sea (representing the European jungles of the Eocene discussed at the beginning of this series) and the island of Hispaniola (which dates to the Oligocene).  Then as now, the Greater Antilles were in the tropics, meaning that the region has not been subjected to the same degree of cooling as much of the rest of the world.  This is confirmed by the fossils themselves; most of the amber on the island is formed from the resin of a relative of the modern algarrobo tree, a tropical legume.  Preserved organisms include organisms such as palms, ants, and lizards, all of which indicate a tropical climate.  Like the Oligocene-Early Miocene sites from Riversleigh, then, the environmental story told by Caribbean amber is not one of organisms and ecosystems adapting to colder climatic conditions.  Rather, amber provides a window on the evolution of one particular ecosystem through time: tropical rain forests.  Rainforests are cradles of biodiversity today and, presumably, through much of Earth's history, but despite their huge importance, they are among the worst-represented biomes in the fossil record.  Decomposition occurs at high rates in jungles and soil conditions are generally unfavorable for preserving many types of fossil (most of the rainforest ecosystems discussed so far this month are actually preserved in lake or marine sediments, which are much better preservational environments).  The rare in situ snapshot of an Oligocene rainforest provided by Caribbean amber allows the study of a forest ecosystem that persists in the area to this day.  To the north, though, formerly forested land was beginning to give way to an entirely new biome dominated by a particularly hearty group of plants and populated by animals forced to play by an entirely new set of rules.

Visit: Caribbean amber is mined commercially, and based on what I can glean from the Dominican Republic's tourism site, none of these mines are open to the public.
Fossils: Two Dominican museums focus on local amber: the Museo Mundo del Ambar in Santo Domingo and the Museo del Ambar in Puerto Plata.  Also in Santo Domingo, the Museo Nacional de Historia Natural has an amber exhibit.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Not as such, but there is a well-written survey of Dominican amber available.

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.

10 December 2015

10. Riversleigh

Nimbacinus dicksoni, a dasyuromorph from the Oligo-Miocene of Riversleigh
Queensland Museum/University of New South Wales
Location: Queensland, Australia
Formation: Numerous
Age: Oligocene-Holocene (25-0 Ma)

Most of the sites included in the Lagerstättenadventskalendar thus far have been from the Northern Hemisphere, in large part because sites in Europe and North America are numerous and have been extensively studied for long periods of time.  However, global climate change, by definition, affects the entire globe and there are sites on the southern continents that document how organisms and ecosystems there were influenced by changing climate.  Perhaps the most significant of these, Australia's Riversleigh is not one site but a series of several in the northwest corner of Queensland.  Riversleigh is remarkable not only because of its location but because it records a history of environmental change encompassing everything from the Oligocene to the present day.  From a preservational standpoint, the most impressive of Riversleigh's fossils are the three-dimensionally preserved arthropods from the Miocene Upper Site, but the most abundant and best-studied of Riversleigh's fossils are its vertebrates.  These include such stars of the Australian fauna as giant dromornithid birds, crocodiles, egg-laying monotreme mammals, and, of course, marsupials.  Everything from (relatively) familiar animals such as koalas and rhino-sized diprotodonts to obscure creatures such as "thingodonts" and tapir- (or possibly sloth-) like palorchestids has been found at Riversleigh.  Of particular interest to me, Riversleigh fossils account for much of what we know about the evolution of the three major groups of Australian carnivorous marsupials: dasyuromorphs (the group that includes Tasmanian devils and most other modern Australian predators), thylacoleonids (the marsupial lions), and propleopines (carnivorous kangaroos!).  Taken as a whole, these fossils and the rocks in which they are preserved tell a long-term story of environmental change from dense rainforest in the Oligocene and Early Miocene to cooler forests in the later Miocene to drier, more open woodland in the Pliocene to the shrubland that characterizes the region today.  No series of sites has provided as much insight into the evolution of Australia's unique fauna and ecosystems as has Riversleigh, and there are few localities anywhere that so clearly tell the story of climatic cooling and drying that characterizes the post-Eocene world.

Visit: The Riversleigh sites have been inscribed as a World Heritage Site and are preserved in Boodjamulla National Park in Queensland.
Fossils: The Queensland Museum in Brisbane is the official repository for Riversleigh fossils, but relatively few are on display there.  This is in large part due to much of the material still being the subject of active research at several institutions across Australia.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: There is!  It's written by Mike Archer, the leading authority on Riversleigh, and his colleagues at the University of New South Wales and, besides being full of gorgeous reconstructions and photos, is an excellent read.

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.

09 December 2015

9. Bridge Creek Flora

The dawn redwood Metsequoia
Photo by staff of John Day Fossil Beds NM
Location: Oregon, USA
Formation: Big Basin Member of the John Day Formation
Age: Oligocene (33 Ma)

The fossil plants of the Big Basin Member in the John Day Basin are only about a million years younger than the fossils of Florissant, but that brief interval of time encompasses one of the most important periods of change in the Cenozoic.  The clock ticked over from the Eocene to the Oligocene 33.7 million years ago, midway between the deposition of the two lagerstätten, and this boundary marks a significant climatological and ecological shift worldwide.  Global temperature had been slowly decreasing through the Late Eocene, but at the boundary it drops precipitously (though exactly how precipitously is still a matter of some debate).  For the first time in the Cenozoic, ice sheets began to grow in Antarctica and ecological turnover occurred across the face of Earth in an event known in Europe as the Grande Coupure.  The plants of Oregon's Bridge Creek Flora very clearly illustrate this new world order.  Though they grew in the same spot where the forests of the Clarno Formation had existed 11 million years earlier, the Bridge Creek plants draw comparisons not to jungles but to temperate deciduous woodlands. The most abundant fossils from these sites are leaves and needles of trees, some - oak, elm, beech, and several others - compare to species from the Southeast US, while others - including ginkgoes and katsuras - have living relatives native to China and Japan.  The most notable of these plants with Asian affinities is the dawn redwood Metasequoia, a deciduous conifer related, as the name suggests, to redwoods and sequoias.  Metasequoia has the distinction of being one of the very few taxa first described as a fossil and to later be discovered alive and well, in this case in the central Chinese province of Hubei.  Its fossils have been found worldwide, but they are especially common in the Bridge Creek Flora and other John Day Basin sites of similar age, leading to its designation as Oregon's State Fossil in 2005.

Visit: Many of the sites from which the Bridge Creek Flora have been uncovered are protected by John Day Fossil Beds National Monument.  One site, behind the football field at Fossil High School, is administered by the Oregon Paleo Lands Institute and allows public collecting for a fee.
Fossils: As with the Clarno Nut Beds, the best place to see Bridge Creek fossils is at the national monument's Condon Fossil Center, which I will reiterate should be near the top of anyone's list of excellent regional fossil museums.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: No, but there should be.

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.

08 December 2015

8. Florissant

Paleovespa, the Florissant wasp
National Park Service
Location: Colorado, USA
Formation: Florissant Formation
Age: Eocene (34 Ma)

The lagerstätten featured so far this month all date to the early or middle parts of the Eocene and, with the rare exception, indicate a global hothouse.  The warm conditions of this interval were not to last, however.  Dating to the very end of the epoch, Colorado's Florissant Fossil Beds are the Eocene's last bow, and suggest that temperate conditions had already become more widespread.  Unlike most other sites in the advent calendar, Florissant preserves some truly massive specimens that document this climatic shift.  The largest fossils from this lagerstätten are redwood trunks that are impressive in and of themselves but that, to anyone who has spent time in the modern forests of coastal California, clearly show that Florissant was no tropical paradise.  Smaller plant fossils, of leaves and flowers, support this conclusion, as they represent trees such as beeches, willows, and pines.  These leaves are preserved in exquisite detail, as are the arthropod fossils for which the site is known.  Perhaps the most familiar of all Florissant fossils is the wasp Paleovespa, but insects from ants to dragonflies (both nypmhs and adults) to katydids have been found there, as have non-insect arthropods (most notably spiders).  Was the cool, lakeside forest occupied by these animals representative of the world as a whole in the Eocene's closing years?  It's worth noting that, like the Okanogan lakes of millions of years earlier, Florissant was a high-elevation site and this likely influenced its climate (its mountainous location certainly had an effect on the site's fossil record, as burial by volcanic ash was a major factor in Florissant's high quality of preservation).  However, the advent of the Oligocene was nigh, and another, slightly younger, lakeside forest shows that temperate conditions were becoming ever more common even at lower elevations in this new epoch.

Visit: The fossil beds are preserved within Florissant Fossil Beds National Monument near Colorado Springs and make a long but doable and worthwhile day trip from Denver.
Fossils: The national monument visitor center has the largest display of Florissant fossils I've seen, but other local museums house specimens as well; I'm given to understand that the University of Colorado Museum of Natural History has an especially large collection.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: There is, and it's another one that my personal collection is sorely lacking.

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.

07 December 2015

7. The Quercy Phosphorites

"Mummy" of the frog Thaumastosaurus gezei
Denis Serrette, Muséum National d'Histoire Naturelle
Location: Quercy, France
Formation: Quercy Phosphorites Formation
Age: Eocene-Oligocene (39-27 Ma)

Phosphorites that outcrop throughout the historic region of Quercy in southern France document life in Europe from the middle Eocene through the later part of the succeeding epoch, the Oligocene.  The earliest of the fossils from Quercy tell a story similar to that told by Messel, though one based largely on remains of vertebrates rather than plants and invertebrates.  Indeed, many of the Quercy specimens are close relatives of Messel taxa and the presence of animals such as parrots and primates shows that even later in the Eocene, Europe remained a much warmer, wetter place than it is today.  Also in common with Messel, the closest living relatives of several Quercy organisms are found today in far-flung locales (such as todies, found today only in the Caribbean and seriemas, now native to the pampas of South America), suggesting that migration between continents was more widespread in the Eocene.  I'm not able to give the Quercy Phosphorites the nuanced coverage they deserve, in large part because most of the published papers on them are in French.  However, I would be remiss if I didn't point out the most remarkable feature of the Quercy fossils, and the aspect of the formation that places it firmly in lagerstätte territory.  The phosphorites have, in several cases, preserved reptiles and amphibians as "mummies" (such as the frog seen in the picture here).  This is unusual and remarkable enough in and of itself, but recent studies that have scanned these "mummies" have shown that besides just skin, the specimens contain skeletons and organs, all preserved in three dimensions, providing insight on soft tissue and internal anatomy usually unavailable from the fossil record.

Visit: The language barrier makes it a bit difficult to confirm this, but as far as I know none of the Quercy localities are open to the public.
Fossils: The main repository for Quercy fossils (including the "mummies") is the Muséum National d'Histoire Naturelle in Paris.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: Oddly no, neither in French nor in English.

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.

06 December 2015

6. Clarno Nut Beds

Plants from the Clarno Nut Beds
Smithsonian Institution
Location: Oregon, USA
Formation: Clarno Formation
Age: Eocene (44 Ma)

One state south of the southernmost Okanogan locality, are the slightly younger Clarno Nut Beds.  As the name suggests, the site is known for its preservation of nuts and seeds, though wood and leaves from plants and a few bits and pieces of animals are preserved as well.  While some of the plants found in the Nut Beds - such as sycamores and conifers - are comparable to those of the Okanogan sites, many indicate a much warmer environment in keeping with other Eocene localities.  Most notable among these taxa are palms, cycads, bananas, and, among animals, the crocodile Pristichampsus.  Why do these nearby lagerstätte represent such different climates?  It likely comes down to elevation: the fossils of the Okanogan were from much higher-altitude, and therefore cooler, ecosystems than their Oregonian counterparts.  There is almost certainly more to the story than this, but these two floras do demonstrate that the overall trend of cooling climate during the Cenozoic is in fact much more complex and that climate can vary considerably across even fairly small regions.  The other noteworthy aspect of the Clarno Nut Beds is their method of preservation.  While most fossils are preserved in sedimentary rocks, the origin of the rocks in which these fossils are preserved is more explosive.  Lahars - mudflows kicked off by nearby volcanic eruptions - raced downhill uprooting and, eventually, burying everything in their path.  Fortunately for posterity, among the things engulfed was a forest, meaning we have a massively destructive event to thank for some of Oregon's most spectacular plant fossils.

Visit: The Nut Beds are preserved in the Clarno Unit of John Day Fossil Beds National Monument, one of the few places in the monument where visitors can view in situ fossils.
Fossils: The monument is also home to the Condon Fossil Center near Dayville, one of the best locally-focused fossil museums you'll see anywhere in the world.  Many Nut Beds fossils are on display here, along with a gorgeous mural depicting the landscape of Eocene Oregon.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?:  No, though the Clarno, along with the rest of the John Day Fossil Beds, is well-deserving of a first-class photologue (if that's even a word).

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.

05 December 2015

5. Lakes of the Eocene Okanogan

Leaf and flower fossils from Stonerose Fossil Site, Republic, WA
Location: Washington, USA & British Columbia, Canada
Formation: Klondike Mountain & Allenby Formations (including Princeton Chert)
Age: Eocene (53-49 Ma)

You all must have known it was only a matter of time before I came to sites from the Northwest (spoiler: this is just the first of many this month).  Messel and the other localities I've highlighted so far may have given you the impression that the Eocene world was entirely blanketed by rainforests.  A series of localities from Washington and British Columbia, though, show that the environmental picture was somewhat more complicated.  The Okanogan Highlands of Washington and British Columbia were even higher in the Eocene, and lakes that formed in the region's valleys have reserved a wide range of organisms.  My favorite Okanogan fossil is the fish Eosalmo driftwoodensis.  Its name translates as 'Dawn Salmon' which is appropriate as it is the oldest and most basal salmon, meaning that the fish synonymous with the Northwest today have been residents of the region since the beginning of their evolutionary history.  In terms of both numbers and quality of preservation, though, the most notable Okanogan organisms are plants (including large specimens of leaves and flowers - most famously from the kola relative Florissantia - as well as microscopic pollen and algae) and insects.  These fossils were first thought to date from the cooler Oligocene Epoch, as they resembled temperate species, but multiple lines of evidence have shown that they date back to the global greenhouse of the Eocene.  How is it that a cool-climate flora lived at the same latitude and time as Messel's crocodiles and primates?  A site a couple of hundred miles to the south helps illustrate the answer to this question.

Visit: Important Okanogan localities are preserved by the BC government within Driftwood Canyon Provincial Park and McAbee Fossil Beds Heritage Site.  These sites are (wisely) off-limits to collectors, but you can collect fossils at the Stonerose site in Republic, WA (though any significant specimens will be retained for study)
Fossils: The Stonerose Center has a display of local fossils.  Elsewhere, the only museum I know of to permanently display several Okanogan fossils is Seattle's Burke Museum.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?:  Not as such, but Spokane author Jack Nisbet has a nice chapter on the Okanogan lagerstätte in his book 'Ancient Places' and paleontologist Bruce Archibald has written a publicly available overview of relevant sites.

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.

04 December 2015

4. Grube Messel

The creodont Lesmesodon behnkeae
Hessisches Landesmuseum Darmstadt
Location: Hesse, Germany
Formation: Messel Oil Shale
Age: Eocene (47 Ma)

A few million years and a hemisphere removed from Fossil Lake, another lakeside rainforest is preserved in a pit mine south of Frankfurt.  Messel is the fossil record's 9th Symphony: immediately recognizable, intensively studied, and sublimely beautiful.  All of the fossils uncovered here - be they plants, invertebrates, amphibians, reptiles,  or birds - are amazingly well preserved, often including soft tissue and detail down to the cellular level.  It is the mammals, though, that really steal the show.  These range from perissodactyls (including pregnant horses preserved with fetuses intact), to carnivores (and their creodont relatives, such as the Lesmesodon pictured here), to primates (such as the much-publicized Darwinius).  Small mammals that are often rare in the fossil record, including rodents, bats, and hedgehogs, are relatively common at Messel, and even some completely unexpected taxa, such as marsupials and pangolins, make an appearance.

Visit: The pit itself, a World Heritage Site, has an excellent visitor's center that can be easily visited as a day trip from Frankfurt, Darmstadt, or Heidelberg.
Fossils: Many museums around the world, especially in Europe, have a handful of Messel specimens.  The largest collections and most impressive exhibits are at the Senckenberg Museum in Frankfurt and the Hessisches Landesmuseum Darmstadt.
Is there a book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?:  There is!  In fact, there are a couple, but one was published as part of a limited run in Germany, so it's a bit hard to find a copy (I can vouch for its being excellent, though).

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.

03 December 2015

3. Fossil Lake

The herring Knightia and palm frond
Field Museum
Location: Wyoming, USA
Formation: Green River Formation
Age: Eocene (50 Ma)

If England and Scandinavia had tropical climates in the Eocene, it should come as no surprise that North America was quite a bit hotter as well.  Perhaps the best evidence for this comes from localities in Wyoming, and no Equality State fossils are more spectacular than those of the Green River Formation.  Palms and crocodiles, many of them spectacularly large and all of them impeccably preserved in the sediments of a series of ancient lakes, attest to the warm, wet climate of what is now an arid landscape.  Fossil Lake has also yielded impressive bird and mammal specimens, including the earliest bat, but the stars of the show are fish.  Literally millions have been uncovered from the shales of southwest Wyoming, ranging from herring and perch to gar and paddlefish and including taxa as exotic as stingrays.  The overwhelming numbers of fish fossils from the Green River Formation mean that they have become common sights in museums, rock shops, and personal collections across the world and making Fossil Lake perhaps the most familiar of all lagerstätte.

Visit: Fossil Butte National Monument near Kemmerer preserves some of the most important Green River localities and has an excellent visitor center.  Several privately-owned sites in the area allow fossil collection (usually for a fee, and remember that poaching fossils from private or public land is a sure ticket to paleo hell).
Fossils: I doubt there is a natural history museum on North America without a Green River collection. The best, and largest, display I've seen is at the Field Museum.
Is there a book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?:  There is!  And, as a subtle hint to my family and friends, this is one of the few books on Cenozoic lagerstätten that I don't own.

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.

02 December 2015

2. The London Clay

Fruit of the palm Nypa burtini
Sheppey Fossils
Location: England, UK
Formation: London Clay
Age: Eocene (54-48 Ma)

Scandinavia isn't the only place with a famously cool modern climate that was home to heat-loving organisms during the Eocene.  Conjure up an image of Victorian London and, especially at this time of year, you probably find yourself thinking of dark, fog-shrouded streets illuminated by the occasional shop window, tavern, or gas lamp.  However, at the same time that authors such as Dickens and Conan Doyle were immortalizing the clammy weather of the great metropolis, paleontologists were beginning to realize that the ground beneath their feet showed that the England of the past was a very different place indeed.  Like the Limfjord moler, the London Clay preserves an Eocene shoreline, and like its Danish counterpart it has yielded several bird specimens, along with fish, invertebrates, reptiles, and even the occasional mammal.  However, it is the plants that have been found in the clay that provide the most unmistakable evidence that southeast England was once much sunnier.  Whereas most of the plant-bearing lagerstätten that I'll be highlighting this month produce primarily leaf and flower fossils, the London Clay tends to preserve harder parts of plants, such as wood, seeds, and nuts.  These fossils reveal a flora in which palms were common, as were relatives of cinnamon, monkey puzzle trees, magnolias, cypress, and other trees associated with warm, wet climates.  This image of a tropical English coast is reinforced by the remains of terrestrial animals such as crocodiles and primates.

Visit: Exposures of the London Clay outcrop throughout southeast England, though to the best of my knowledge there is no museum or interpretive center devoted exclusively to it.
Fossils: Most museums in England have at least a few London Clay fossils.  The largest exhibit I recall seeing is at the Sedgwick Museum in Cambridge.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: No, but there are several monographs on fossils from the clay, some dating back to the 19th Century.

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.