The Saltville Fossil Site in Virginia

A dense forest of white pine, spruce, fir, and oak  grew in the Saltville River Valley 17,000 years ago.  There were also some alder swamps and wet sedge meadows, but unlike in the regions to the south and west of this locality, there were no prairies or open woodlands.  The Saltville River Valley is located in southwestern Virginia and during the last Ice Age, this area was much colder than the region located immediately to the south.  The oceanic Gulf Stream that carries tropically-warmed water north as far as the Canadian coast today, instead only went as far north as the Virginia/North Carolina border during the Ice Age.  This meant dry land temperatures in what is now Virginia were as much as 10-15 degrees Fahrenheight  cooler on average than those about 50 miles  further south.  Consequently, the environment in the middle Atlantic States decisively differed from most of southeastern North America.

Location of the Saltville River Valley.

Saltville, Virginia is located in a beautiful valley.  A large lake, known as Lake Totten, covered much of the valley from ~13,500 BP-~8,500 BP.  Salt mining operations have upset the hydrology here, and today as much as 20% of the valley is underwater. 

The Ice Age began waning about 15,500 years ago.  The Laurentide Glacier slowly receded, and the melting ice increased the flow of water into the Saltville River.  Sediment carried by the increased flow formed a mud dam in the Saltville Valley gap, causing the water to backflow and create Lake Totten.  The outflow was captured by another river.  Many of the species of large mammals that lived in North America then were attracted to the abundant salt springs in the area.  The individuals that happened to die during periods of increased sediment flow were buried by mud and preserved for fossil enthusiasts and scientists to find thousands of years later.

An assortment of fossils found at Saltville.  The animals were buried by mud carried by river surges resulting from melting glacial ice to the north.  Paleontologists have to pump out groundwater from their excavation sites here.  Salt mining operations have caused much of the land to flood.

The Saltville fossil site is the most southerly known location where specimens of woolly mammoth (Mammuthus primigenius) have been excavated.  Specimens of Columbian mammoth (Mammuthus columbi) have been excavated here too, showing the 2 species co-existed in some locations.   The 2 species of mammoth have also been found together at a site in South Dakota.  Columbian mammoths ranged much farther south than woolies, having occupied territory as far south as what today is Florida.  Other megafauna species recovered at Saltville include mastodon, Jefferson’s ground sloth, woodland musk-ox, bison, stag-moose (Cervalces scotti), caribou, white tail deer, horse, and giant short-faced bear (Arctodus simus).   Scientists have yet to publish their findings on the smaller species of animals discovered in the fossil deposits.

Puncture mark on a mammoth heal bone made by a giant short-faced bear’s canine.

Gnaw marks on an ankle bone, probably made by a dire wolf.

A mammoth heel bone excavated from this site has a puncture mark that matches the canine of a giant short-faced bear.  This species of bruin is thought to have specialized in kleptoscavenging.  (See: https://markgelbart.wordpress.com/2012/12/10/bearzilla-the-biggest-bear-in-history/) The ankle bone of the same animal was gnawed on by a canid, probably a dire wolf.

A study of the bone chemistry of fossil herbivores from this site had an unexpected result.  All the herbivores living in this region then ate C-3 (carbon 3) vegetation–trees, shrubs, and some herbs.  Even species such as mammoths, bison, and horses that predominately subsisted on C-4 vegetation (grass) elsewhere were restricted to a diet of twigs, leaves, bark, and herbs here.  This is considered evidence that prairies were absent from this particular region during this time period.  The authors of this study admit their findings weren’t sufficient evidence to make any conclusions about megafauna extinctions.  Yet, they suggested competition between grazers and browsers for the same resources may have caused megafaunal extinctions.  I disagree with this conjecture.  Instead, I think their findings are strong evidence against climate change as a cause of megafaunal extinctions because the study shows these animals were not picky eaters and could adapt well to changing environmental conditions.

Humans apparently killed, butchered, cooked, and ate a mastodon at Saltville 17,000 years ago.  Archaeologists found cut marks on a mastodon’s bones as well as congealed grease that could only be the result of cooking.  They also found heat-cracked rocks used in the cooking process.  Pre-Clovis artifacts found associated with the mastodon bones include 2 sandstone knives, a chert blade made out of rock transported from some distance away, and flakes (debitage) from tool-making.  The site was occupied 3 times prior to the Clovis era.  The most recent pre-Clovis horizon dates to about 15,000 years ago and includes a midden containing hundreds of shells from giant floater clams.  This species of freshwater mussel grows to 10 inches long and used to be abundant in North American waters before modern day pollution and river damming.

Giant floater clam (Pyganodon grandis).  I’ve never eaten a freshwater mussel, but they smell like delicious oysters.

Saltville is not a new site.  Thomas Jefferson knew about fossils found here.  Scientists have been excavating fossils off and on here for over 200 years.  A team from East Tennessee State completed the most recent excavation this year.  They visited local amateur fossil collectors to examine their specimens, and they are surveying caves in the nearby mountains in the hopes of finding more fossils to help piece together the regional late Pleistocene ecology.  We haven’t heard the last about this site.

References:

France, Christine; et. al.

“Carbon and Nitrogen Isotopic Analysis of Pleistocene Mammals from the Saltville Quarry (Virginia USA): Implications for Trophic Relationships”

Paleogeography, Paleoclimatology, Paleoecology 249 2007

Schubert, Blaine; and Steven Wallace

“Late Pleistocene Giant Short-Faced Bears, Mammoths, and Large Carcass Scavenging in the Saltville Valley of Virginia, USA”

Boreas 38 (3) August 2009

The South Central Salient of the Helmeted Musk-ox (Ovibos cavifrons or Bootherium bombifrons)

Portrait of the woodland or helmeted musk ox from the Illinois Museum of Natural History

The way scientists assign scientific names to extant and extinct species can be confusing.  The rule is simple–the scientific name given by the scientist who first describes the first specimen ever discovered (also known as the “type specimen”) is the one that supercedes all other later names.  Complications arise when other scientists discover new fossil material of the same species and mistakenly believe they’ve discovered a new species, and they assign a completely different scientific name to the specimen.  Decades often pass before other scientists compare the fossils and determine they’re one and the same species.  The extinct helmeted musk-ox provides a case study of this confusion.  Scientists discovering fossils of this wide-ranging species from all over the continent have assigned many different scientific names to this species including Bos bombifrons, Bootherium bombifrons, Symbos cavifrons, Ovibos cavifrons, Bison appalachicolus, Liops zuniensis, Symbos australis, Bootherium nivicolum,  Symbos converifrons, Ovibos giganteus, and Bootherium brazosis.  This sounds like a joke, but it’s not.  It created a real mess for later scientists to straighten out.

Fossil hunters first found a helmeted musk-ox fossil in 1804 at the Big Bone Lick Fossil site in Kentucky.  The first scientist to look at it put it in the Bos genus which is the same one domesticated cattle belong to.  It wasn’t until 50 years later that it was recognized as a type of musk-ox.  Extreme sexual dimorphism caused the proliferation of species names for just one animal.

The horns on a male helmeted musk-ox were much larger and robust than those on the female.  Scientists mistakenly thought they were from two different species.  Note the difference between the male and the female horns (f & e) in this diagram.  Diagram from the below referenced paper written by R. Dale Guthrie.

Male helmeted musk-oxen are so much larger than females that for a long time scientists believed they were seeing different species: males were classified as Symbos cavifrons, and females were classified as Bootherium bombifrons.  Finally, in a paper written in 1989 Jerry McDonald and Clayton Ray thoroughly studied all the fossil material and determined they were one and the same species.  Because Bootherium bombifrons was the older name, that is now considered the official scientific name for the species.  I mistakenly thought Ovibos cavifrons was the official name, and it makes sense because its close living relative, the woolly musk-ox goes by the scientific name of Ovibos moschatus. It seems the woolly and helmeted musk-ox should be in the same genus, but they’re not.

I’ve noticed a curious geographical distribution of helmeted musk-ox fossils.

Distribution map for helmeted musk-ox.  This map includes just the skulls, so I added a dot for a musk-ox fossil found in Nashville, Tennessee, and drew the line to illustrate the salient.  Helmeted musk-ox must have been an adaptable animal to range this far.  Map from the below referenced paper written by McDonald and Ray.

Helmeted musk-oxen fossils come from Bayou Sara in south central Louisiana, Texas, and Mississippi north to Alaska and west to northern California and east to the continental shelf off what today is New Jersey.   Their range seem to have extended south along the Mississippi River.  A south central salient of its range is notable.  Fossil sites in the piedmont region of the southeast are so rare there is no telling where its southeasternmost range occurred.  None have been found in Florida’s abundant sites, indicating its probable absence there.  Fossil sites in Nashville, Tennessee and Saltville, Virginia yield helmeted musk-oxen specimens, but it may have been absent from the southeastern coastal plain.  Looking at the line I drew on the above map, it’s likely helmeted musk-oxen did range over northern Alabama and the ridge and valley region of northwestern Georgia. 

If they could survive the warmer climates of Mississippi, Louisiana, and Texas, it couldn’t have been climate that prevented them from colonizing the southeastern coastal plain.  Perhaps, because long-horned bision were already abundant here and occupied a similar niche, helmeted musk-oxen never could become established.  Maybe, it’s just chance they never migrated into the region.  Or maybe they were present but in such low numbers as to be invisible in the fossil record. 

The extinct helmeted musk-ox differed from the living woolly musk-ox in many characteristics.  As evident from its much wider range, the helmeted musk-ox was much more adapatable.  It had longer legs allowing it to run greater distances and with more speed.  It was taller and more slender, suggesting it had more endurance.  Scientists found fur on one specimen.  The hair was shorter and finer–evidence that it did not have a heavy woolen coat like its living cousin.  The two species did coexist in parts of Alaska and unglaciated Canada, but Dr. Guthrie sees evidence of habitat parturation.  Helmeted musk-oxen lived in arid grassy steppes in this region whereas woolly musk-oxen inhabited more mesic tundra.  Dr. Guthrie favors the common name helmeted musk-ox over woodland musk-ox because the species was just as likely to be found on grassy steppes and savannahs as open parkland woods.  I agree with him and from now on will refer to it on this blog as the helmeted musk-ox.

Evidence from fossilized feces and plant fragments in fossil teeth show that helmeted musk-oxen ate a wide variety of plant foods including sedges, grasses, blueberry bushes, and willow twigs.  In fact one sample of fossilized dung consisted of nothing but willow twigs.  Some times their feces was pelletized.  Dr. Guthrie states that this is evidence of a capability to eat a lot of dried plant foods without having to eat snow for water.  It’s an adaptation of moisture conservation, enabling the species to survive frigid arid environments. 

Helmeted musk-oxen were able to live in temperate climates where human populations eventually became high.  I believe this is the reason they became extinct while woolly musk-oxen avoided human overhunting in remote regions of the arctic.  It’s ironic that an animal that was more adapatable died out because of this adaptability.  I disagree with scientists who think natural environmental changes caused their extinction.  This highly adaptable animal enjoyed a wide range during the Pleistocene as the above map shows.  This means they inhabited a great variety of habitats from Alaskan grassy steppe to prairies to open forests interspersed with meadows.  Suitable environments  for helmeted musk-oxen, especially in the midwest and upper south, never completely disappeared.  The foods they ate–grasses, sedges, blueberry bushes, willow trees–always remained abundant throughout much of the continent.  Moreover, their fossils are known from deposits as old as 300,000 years BP, meaning they survived previous transitions from glacial to interglacial.  I see no change in the environment that would cause their extinction, other than the increase in the number of people hunting them.  Dr. Guthrie suggest bison outcompeted musk-oxen on the prairies, but this makes little sense–musk-oxen and bison coexisted for hundreds of thousands of years.

Woolly musk-oxen survived extinction because they inhabit remote regions of the arctic.  Even here, human hunting reduced their numbers.  Human hunters wiped out woolly musk-oxen  in Alaska before the introduction of firearms, though the beasts have been reintroduced here.  Still, there are large areas of suitable habitat in Alaska where woolly musk-oxen are absent due to human hunting.   During the Ice Age woolly musk-oxen were more widespread living as far south as Spain.  Undoubtedly, climate change and the resulting contraction of barren tundra has played a role in diminishing habitat for this species, but suitable habitat for helmeted musk-oxen expanded following the retreat of the glaciers, especially in the midwest.  Suitable habitat in the upper south remained the same. 

I hypothesize men exploited the musk-ox’s habit of standing in a defensive circle to face down predators.  It may prove effective against wolves or big cats as long as they don’t panic and begin running (as seen in this video http://www.youtube.com/watch?v=pb6Rke7jiTc ) but it was catastrophically fatal for helmeted musk-oxen when a gang of humans confronted them.  Humans could use projectile weapons to slaughter entire herds standing stationary in one place.

Some scientists claim the scant evidence that humans hunted helmeted musk-oxen suggests they played no role in their demise.  This argument frustrates me.  There isn’t a single skeleton of a human from the Clovis era in North America.  Why should we expect to find remains of their meals?  Nevertheless, there is some evidence of humans exploiting helmeted musk-oxen.  Clovis age arrowheads associated with musk-oxen bones and with bovine blood on them were found at the St. Mary’s reservoir in Alberta, Canada.  And a human “modified” musk-oxen bone turned up at the fossil site in Saltville, Virginia (a pre-clovis site).  Scientists who argue against the human overkill model of extinction never say how much evidence would be enough to convince them.

References:

Guthrie, R. Dale

“New Paleoecological and Paleoethological Information on the Extinct Helmeted Musk-oxen from Alaska”

Ann. Zool. Fenninci 28: 175-186 Feb. 1992

McDonald, Jerry; and Clayton Ray

“The Autochthonous North American Musk-Oxen Bootherium, Symbos, Gidleyea (Mammalia: Artiodactyl: Bovidae)”

Smithsonian Contributions to Paleobiology #66 1989

The Lost Pleistocene World of the Georges Bank

I’m taking an imaginary vacation this week away from southeastern North America to visit one of the few ice free spots in the northeast during the Last Glacial Maximum.

The Georges Bank used to be one of the richest fisheries in the world.  During the LGM it was an extension of the mainland inhabited by many species of megafauna.

East of the Gulf of Maine the sea floor rises 330 feet.  Both cold and warm currents sweep over this submerged island, and light can reach the shallow bottom which ranges between 10-50 feet deep.  The light and the mixture of currents create an ideal habitat for a rich zone of phytoplankton.  The phytoplankton  is the foundation of a food chain that feeds over 100 species of fish, and the gravel bottom, eroded from glacier-pushed rocks, provides excellent spawning structure.  One of the richest fisheries in the world used to be found here before fleets of international factory ships decimated the naturally abundant stocks in the 20th century.  Long before Basque fishermen discovered this amazing fishing ground in the 11th century, the Georges Bank existed as a special and beautiful part of the North American mainland.

20,000 years ago, a massive glacier, one mile thick, depressed the entire area of what’s now New England.  The weight of all that ice literally pushed the earth’s crust down.  Glaciers from previous Ice Ages had already gouged a trough off what today is Maine’s coast, explaining why the Gulf of Maine is so deep.  The most recent glacier, the Laurentide, advanced over the dried-out trough toward the receding Atlantic Ocean.  The ocean was receding because so much of the world’s water was becoming locked up as ice.  But on the narrow strip of higher land in the vicinity of the Atlantic Ocean, the climate was warmer, perhaps keeping the glacier at bay.

The Georges Bank was an extension of the mainland, 140 miles long and 75 miles wide.  It was bounded on one side by the enormous glacier, and on the other by the ocean.  The climate consisted of cool summers, thanks to the monstrous ice cube next door, and snowy but bearable winters because moderating oceanic winds prevented temperatures from plummeting as low as occurred farther inland.

Icebergs drift off shore here within site of the sand dunes where beach grass, beach pea, and bayberry grow.  Walruses swim to and fro from small ice floes to the beach.  Behind the beach dunes, brackish lagoons host ducks and geese and loons.  Forests of pine, spruce, fir, birch, and alder cover most of the island, interrupted here and there with cranberry bogs.  Grassy windswept steppes are located on the northern part of the island and on nearby Sable Island.

Tim Wichinbach dredged up this partial mastodon tusk while fishing for scallops over the Georges Bank.  Fishermen have accidentally caught Pleistocene fossils in their nets in more than 40 sites on the Georges Bank.  The list of accidental bycatch includes fossils of mastodon, mammoth, woodland musk-ox, stag-moose, long-nosed peccary, walrus, bearded seal, and wood from ancient forests.  Reportedly, tapir and ground sloth bones have also been dredged, but I can’t find documentation in the scientific literature.  A good comprehensive catalogue of Georges Bank fossils has not been published.  Information is limited to 3 old articles from very obscure scientific journals.

An early October snowstorm covers a north facing slope, yellow grass tufts stick above the white layer.  A herd of dwarf mammoths and lean musk-oxen graze on the grass, the mammoths clearing the snow with their tusks.  The horns on the musk-oxen cover their skulls like football helmets.  Closer to a forest edge in a low lying area on the other side of the slope, steam rises from a bog.  A huge solitary stag-moose stands ankle deep, a mouthful of green slime hangs from his mouth.  I think it’s a clump of duckweed.  In the open forest mastodons use their trunks to tear branches from young spruce and red pine saplings.  I can hear them grind the cellulose between their giant molars.  One of the hairy elephants has an itchy hindquarter.  He backs up against a jack pine and rubs, but it’s a dead rotten tree, and it snaps and falls over, startling a spruce grouse which flies away in panic.

5,000 years later, the climate warms, and the Laurentide glacier melts as rapidly as 300 meters a year.  Birch forests colonize the newly available land, and the animals follow, but soon, rising sea levels inundate not only the Gulf of Maine, but areas of the coast that are currently above sea level, including the future sites of Augusta and Bangor.  As the heavy weight of the glacier recedes, the land area of Maine rebounds because there is nothing pressing the earth’s crust down here any more.  This is known as isostatic rise.  Meanwhile, the Georges Bank has become a true island, surrounded by ocean water on all sides.  Eventually, sea levels rise more, dooming the animals that didn’t migrate west.  The Grand Banks to the north also falls below sea level.  Only a small spit of sand, the highest point of Sable Island, still remains above sea level in this region.

A Sad Timeline of the Rape of the Georges Bank Fishery

The Georges Bank was an astonishingly rich fishery.  When first discovered by Basque fishermen around 1000 AD, they kept it a secret for over 500 years.  Cod were so abundant fishermen could just stick a basket in the water and 50 pound cod would fill it immediately.  Early colonists living near Cape Cod complained about having to eat lobster every night.  The cod take continued to remain strong until the 20th century when industrial ships from all over the world caught thousands of tons of fish.  Finally, in 1977 the U.S. banned foreign trawlers but it was too late.  American fishermen continued to overfish and now there’s little left–a testament to man’s shortsighted greed.  It’s another sickening example of poor natural resource management.

1830–Right whales nearly exterminated

1850–Halibut disappear

1977–Herring fishery collapses

1994–Commercial cod fishing collapses.  Law passed to outlaw commercial cod fishing proves ineffective.  It’s still not policed.

In my opinion all commercial fishing on the Georges Bank should be banned for 20 years.  Maybe then, it would recover.