The Squirrel-Conifer-Fungi Connection

The evolutionary divergence of the northern flying squirrel (Glaucomys sabrinus) from the southern flying squirrel (G. volans) is an excellent example of speciation resulting from environmental change.  Genetic studies suggest both of these American species of flying squirrels diverged from Eurasian flying squirrels between 4-6 million years ago.  Eurasian flying squirrels are much more diverse and include 44 species, most of which live in southeast Asia–evidence this part of the world is where they originally evolved.  During the late Miocene about 5 million years ago, a forested landbridge connected Asia with America, explaining how the ancestor of both American species of flying squirrels colonized this continent.  Genetic evidence suggests the 2 American species of flying squirrels diverged from each other early during the Pleistocene between 1-2 million years ago when Ice Ages began to become more severe.  Boreal spruce forests expanded during Ice Ages, growing as far south as middle Georgia and Alabama.  In the middle south spruce forests grew in higher elevations while deciduous oak forests still occurred in adjacent lower elevation.  Oak forests are rich in mast such as acorns and nuts, but spruce forests offer less food for squirrels–seeds from spruce cones are only available for 2 months of the year.  However, underground fungi, also known as truffles, are available year round in spruce forests.  For most species of squirrels, fungi is a minor component of their diet, but truffles and other fungi make up 85% of the northern flying squirrel’s diet whereas southern flying squirrels eat more acorns, nuts, berries, and animal matter.  The ancestors of the northern flying squirrel were those individuals from the parent population best able to subsist on a diet of mostly fungi.  These individuals were able to colonize spruce forests, while the rest of the parent population remained in oak forests.  Eventually, this habitat partition resulted in a divergence between the 2 American species.

Northern flying squirrels eat mostly fungi which is a minor component in most squirrel’s diet.  The ability to subsist on a diet of mostly fungi enabled this species to colonize spruce forests.  Eventually, they evolved into a different species than southern flying squirrels because of this capability.

Elaphomyces or truffle–favorite food of the northern flying squirrel.

 

 

Red spruce (Picea rubens).  Red spruce, truffles, and northern flying squirrels are beneficial and interdependent to each other.

Fossils of both species of flying squirrels have been found at Ladds and Kingston Saltpeter Cave in Bartow County, Georgia.  This is evidence that patches of spruce forest grew near patches of oak forest in this region during some climatic stages of the Pleistocene.  Northern flying squirrels are confined to the former; southern flying squirrels require the latter.

There is an interesting ecological interdependence between northern flying squirrels, red spruce, and several species of fungi.  Truffles grow intertwined with the red spruce roots, and they exchange nutrients.  The squirrels eat the truffles and spread their spores throughout the forest in their droppings.  A healthy spruce forest requires an abudance of truffles.  Many red spruce forests have been logged, and without the squirrel’s help, trees such as oak, maple, beech, and cherry are replacing them.  In West Virginia the U.S. Forest Service has successfully re-established red spruce forests.  Foresters discovered that red spruce seedling grow best in ground ripped apart by bulldozers and strewn with woody debris.  Some of these young spruce forests are on land reclaimed from strip mining. 

 

Fox squirrel.  This species may play a role in distributing fungi in longleaf pine savannah. 

Rhizopogon nigrescens–a fungi common to longleaf pine savannahs and likely an item in the diet of the fox squirrel.

Virgin stand of longleaf pine (Pinus palustris) in east Texas (circa 1908).

Although fox squirrels (Scirius niger) have a much more varied diet than northern flying squirrels, they occasionally eat fungi and may play a role in the health of longleaf pine savannahs.  Certain kinds of fungi that grow in the soil of savannahs also exchange nutrients with longleaf pine trees, and fox squirrels spread these spores in their dung as well.  Fox squirrels and longleaf pine savannahs were formerly common in the south, particularly on the coastal plain, but today both are rare.  The changes man has wrought have really sickened the natural communites of the world.

Reference:

Arbogast, Brian

“A Brief History of the New World Flying Squirrel: Phylogeny, Biogeography, and Conservation Genetics”

Journal of Mammalogy 88 (4) 2008

Advertisement

The Mystery Cat of Pleistocene Georgia

Most small species of cats are adept tree climbers, but the margay (Leopardus wiedii) excells. It hunts, copulates, and raises its young in trees, making it as arboreal as a monkey or squirrel.

The margay is about the size of a large house cat.  It is an arboreal species.

The margay is able to climb head first down trees, and its wrists are built much like those of a squirrel’s.  Click on the below link to the youtube video of a margay.  Note how it can hang upside down using just its rear paws.  Note also its athletic ability to leap from tree limb to tree limb.

http://www.youtube.com/watch?v=ef129AsFfMA

The margay is a nocturnal hunter, preying upon birds, birds’ eggs, frogs, lizards, rodents, monkeys, and probably bats.  They also eat fruit.  Like tigers, they use audible mimicry to lure prey.  They’ve been observed imitating the cries of a baby monkey to attract parent monkeys to their doom. (Tigers imitate the mating bugle of elk.)  Not all prey is defenseless, however.  Brazilian squirrels gang together and drive margays away.

Today, the margay ranges throughout Central and South America, but fossil evidence of a margay-like cat has been found from 12 sites in Florida and 2 in Georgia.  Jaw bones of this mystery cat come from Ladds in Bartow County, Georgia and the Isle of Hope site in Chatham County near Savannah–evidence this species occurred throughout the state during the Pleistocene.  The fossils from all the sites where this species has been found likely date from a warm interglacial period.  Some scientists think these fossils represent an extinct species (Leopardus amnicola), while others consider it an extinct, large subspecies of margay (Leopardus wiedii amnicola).  The modern margay requires dense forest habitat, and it’s likely this species or subspecies did too, probably explaining why its fossils are found in deposits dating to interglacial periods.  During interglacials forested habitats expanded.

Sketch of the jaw bone of a cat found at the Ladds fossil site.  Click to enlarge.  Dr. Clayton Ray thought this specimen was most like the jaw bone of a jaguarundi, but other scientists have concluded it’s from a cat that was more like a margay.  This page is from the below referenced paper authored by Dr. Ray.

Photo of a jaw bone of a cat found at the Isle of Hope site near Savannah, Georgia. Click to enlarge.  Every measurement of this specimen falls within the size range of both margay and jaguarundi.  This means it can’t be conclusively identified.  It’s slightly smaller than most specimens identified as Leopardus amnicola.  Page from the below referenced study authored by Dr. Hulbert.

The ocelot (Leopardus pardalis) is about the size of a bobcat or maybe a little larger is some cases.  Unlike the margay, it’s primarily a ground dweller, though it can climb trees.  It mostly feeds upon rodents.  Today, ocelots range throughout Central and South America and rarely into south Texas and Arizona.  In the 19th century, they were found in Louisiana and Arkansas, and fossil evidence of this cat has been found from 2 sites in Florida, also probably dating to a warm interglacial.

The ocelot and margay shared a common ancestor.  It’s likely that some individuals of this ancestral species preferred hunting on the ground and their decendents evolved into ocelots, while other individuals preferred hunting in the trees and their decendents evolved into margays.  Males that were good tree climbers were more likely to meet females that were good tree climbers, and they passed on the beneficial genes that gave them their natural ability.

The ocelot can grow to a size as heavy as 40 pounds.  Also used to range into southeastern North America.

The jaguarundi (Puma yagaouroundi) is a 3rd species of small neotropical cat.  It was formerly classified in its own genus by some scientists and lumped in the Leopardus genus by others, but genetic studies suggest it is closely related to the cougar (Puma concolor).  I hypothesize that an isolated population of cougars began specializing in small prey to avoid competition with larger carnivores such as jaguars, saber-tooths, and lions.  This population then evolved into jaguarundis.  Studies show cougars regularly take smaller prey than jaguars, and there isn’t much overlap in their prey selection.  In some locality with scarce prey, competition may have forced the ancestral population to take even smaller prey.  Today, the jaguarundi preys upon birds, rodents, opposums, small species of deer (brocket), reptiles, and insects.  It eats fruit as well.  It ranges throughout Central and South America and rarely south Texas.  100 years ago, some were introduced to Florida, and a small population may still exist there.  Reported sightings continue.

The jaguarundi may have ranged into southeastern North America as well.  It’s also known as the otter cat due to its cylindrical shape.  It’s closely related to the cougar but is about 10% its size.

It’s evident at least 2 species of neotropical cats colonized southeastern North America during warm climatic phases of the Pleistocene.  I hypothesize that they continued to live in the region until approximately 28,000 BP.  Dense forests remained widespread in the region until then.  Between ~28,000 BP-~15,000 BP prairies, desert scrub, and spruce woodlands replaced the kinds of forests margays and ocelots prefer, though it’s possible they persisted near the coast where ocean currents kept the climate from deteriorating.  If it wasn’t for man, I think ocelots and margays would have recolonized the south.  Fossils of margays have been found in Texas, and they date to 4400 BP, showing they were more widespread recently.  However, native Americans coveted their beautiful coats, and I suspect human hunters prevented the re-expansion of their range.

References:

Hulbert, Richard; and Ann Pratt

“New Pleistocene (Rancholabrean) Vertebrate Faunas from Coastal Georgia”

Journal of Vertebrate Zoology 18 (2) June 1998

Ray, Clayton

“Pleistocene Mammals from Ladds, Bartow County, Georgia”

Georgia Academy of Science Bulletin 25 (3) 1967

If I could live in the Pleistocene part XI–The Turtle trap and my Pleistocene Pot Party and Playlist

In this irregular series “If I could live in the Pleistocene…,” I imagine what my life would be like, if I could travel back in time to ~39,000 BP and live in the geographical area later to be known as central Georgia but with some selected modern conveniences I brought  with me.  I constructed an adobe home that is sort of like a mini-castle with a watchtower and a high stone fence surrounding a farm where I raise and grow most of my own food.  I generate my own electricity and even have wires going through the time tunnel so I can communicate with the modern world.  I enjoy an idyllic life of farming, hunting, and fishing in a pristine wilderness that exists before man ever colonized the region.  I located my home about a mile north of the Broad River for ready access to fish and aquatic animals.  On previous segments of this series I’ve discussed fish traps and turkey traps.  Today, I’ll show how I catch turtles and discuss the species usually found in my traps.

My last adventure (https://markgelbart.wordpress.com/2012/11/02/if-i-could-live-in-the-pleistocene-part-x-turning-a-bear-into-soap/) in November was the dilemma I faced when I ran out of soap and my concubines wouldn’t sleep with me until I made a new supply.  I ended up having to kill a big old bear  in order to get enough animal fat to make soap.  We spent the winter eating hamburgers made out of a blend of bear meat and venison.  Water levels were too high for fish and turtle trapping, but spring is here and the river level dropped.  We’re ready for a change in our diet.  The fish trap provides more food than we can eat, but we want something different.  Fortunately, catching turtles is just as easy as catching fish.  I simply constructed a small cage made out of chicken wire and attached 2 styrofoam floats to it.  The cage has no top.  Instead, a piece of wood is placed on 1 side and suspended over  the cage. A spring holds the piece of wood over the top. When a turtle crawls on the wood over the cage, its weight causes the wood to teeter, and the turtle falls into the cage.  The spring snaps the wood back in place, ready for the next turtle.

Illustration of a turtle trap.  The turtle crawls on the suspended wood to sun itself.  The wood acts like a teeter-totter and drops the turtle into the trap.  A spring snaps the wood back into place.  I place my trap in a shallow part of the river and anchor it down.

The most common kind of turtle found in my trap is the river cooter (Pseudemys concinna).  It’s also known as the chicken cooter because it affords about as much meat as a chicken.  It was a common source of protein for slaves on southern plantations before the Civil War.  Chicken cooters are omnivorous but mainly feed upon aquatic vegetation.  During winter they burrow into mud at the bottom of a water course and literally breathe through their ass–their cloaca can absorb oxygen from the water.  In real life chicken cooters are still abundant, especially in suburban ponds where humans have forgotten they are good to eat.

River or chicken cooter.

I also catch Florida red-bellied turtles (Pseudemys nelsoni).  Florida red-bellied turtles have an interesting distribution history.  Today, this species is restricted to Florida and extreme southeastern Georgia.  (An introduced population thrives on the San Marcos, River in Texas.)  However, fossils of this species were found at the Ladds site in Bartow County, Georgia about an hour north of Atlanta.  The Ladds site likely represents the Sangamonian Interglacial interval.  Florida red-bellied turtles were once more widespread through the south.  Moreover, there are also 2 geographically distinct but closely related species of red-bellied turtles–P. rubriventis of the mid-Atlantic states and P. alabamensis of southern Alabama and Mississippi.  Red-bellied turtles prefer ponds and still waters rather than rivers.  This habitat preference may explain why there are no red-bellied turtles living within a range they used to inhabit.  Red-bellied turtles must have difficulty dispersing following environmental changes that result from climate perturbations.  Arid climate during the Last Glacial Maximum reduced available aquatic habitat, and red-bellied turtles have since failed to reoccupy much of their former range.

Florida red-bellied turtle.

Range map of Florida red-bellied turtle.  Before the LGM they had a broader range across the south.  They have so far failed to recolonize their former range since the Ice Age.

Soft-shelled turtles (Apalone spinifera) fall into my trap.  This large predatory species is just as aggressive as a snapping turtle, and they have a longer neck, so I have to be careful when handling them.  They feed upon fish, frogs, and ducks. They are surprisingly fast.  In real life I once saw a soft-shelled turtle running down a hillside, and it demonstrated blazing speed–I think faster than a rabbit.  So much for the tortoise and the hare myth.

Soft-shelled turtle. They grow to 40 pounds.

Snapping turtles (Chelydra serpentina) weigh up to 35 pounds, and when I catch 1 of these, I have extra meat for my freezer.

Snapping turtle feeding on a bream.

Turtle meat tastes like lobster.  In real life I found turtle meat for sale at a Kroger supermarket seafood department.  It was imported from New Zealand.  (Americans can’t even raise their own turtles?)  I made a delicious catfish and turtle stew.

Turtle and catfish stew.  Has potatoes to make it substantial.  Seasoned with chili powder, bacon, and onion.  Delicious.

I’m not going to go into all the gruesome details of killing and butchering the turtles I caught.  I put some into a tank to be fed a special clean diet until we’re ready to eat them, but I did kill and clean a medium-sized snapper.  It’s important to wash hands when handling turtles because they carry salmonella just like chickens.  Some turtles provide a bonus–unlaid eggs.  Turtle eggs are good for cooking and make for rich cookies and cakes, but they have an unusual property.  The whites of turtle eggs never get hard, no matter how long they are boiled.  The white remains liquid around the hard yolk.

While my turtle stew is slow-cooking on the stove, I decided to get high and listen to music before supper.  I carried a big stein of home-made beer (made with barley and hops I grew) and a joint of my  marijuana (which I also grew on my Pleistocene farm) to the top of my 5-story castle watchtower, constructed in the shape of a lighthouse, where I can observe the wilderness surrounding my home.  This is my favorite kind of party: listening to music undisturbed by anybody–even my concubines leave me alone and stay downstairs.  I flip on the tunes, enjoy the scenery, and get wasted.  If I went back in time, I’d have to bring rock and roll music with me.  Here’s my Pleistocene playlist.  (Realize this: I play these songs in exact order while I keep getting more and more wasted.)

“Oh Carol” — Chuck Berry showing Keith Richards how to play the song.http://www.youtube.com/watch?v=PEA6gzAAPfc

“Can’t you hear me knocking”–Rolling Stones

“It’s only Rock and Roll”–Rolling Stones

“Got to get you into my life”–Beatles

“Yer Blues”–Beatles

“I am the Walrus”–Beatles

“You gotta fight for your right to Party”–Beastie Boys

“Low”–Cracker

“Longview”–Green Day

“Brain Stew”–Green Day

“Delivering the Goods”–Judas Priest

“Devil’s Child”–Judas Priest

“Living after Midnight”–Judas Priest

“Falling in Love”–Scorpions

“Loving you Sunday Morning”–Scorpions

“Animal Magnetism”–Scorpions

“Chained”–Van Halen

“Hot for Teacher”–Van Halen

“Heavy Metal”–Sammy Hagar

“Flying High Again”–Ozzy Osbourne

“No More Tears”–Ozzy Osbourne

“Sweet Leaf”–Black Sabbath

“Fairies Wear Boots”–Black Sabbath

“Still Raining, Still Dreaming”–Jimi Hendrix

“Freedom”–Jimi Hendrix

“Ezy Ryder”–Jimi Hendrix

“How Many More Times”–Led Zeppelin

“The Lemon Song”–Led Zeppelin

“Rock and Roll”–Led Zeppelin

“Over the Hills and Far Away”–Led Zeppelin

“Custard Pie”–Led Zeppelin

“For your Life”–Led Zeppelin

“I Can’t Quit You”–Dred Zeppelin

“Oh Darling”–Beatles

“Big Love”–Robert Plant

“Radioactive”–The Firm

“Social Disease”–Elton John

“Dan Dare: Pilot of the Future”–Elton John

“Funeral For a Friend/Love Lies Bleeding”–Elton John

“Spanish Flea”–Herb Albert

“Rise” –Herb Albert

“Can’t Keep My Eyes off of You”–Frankie Valli

Sex cures hangovers.  Excessive alcohol consumption causes an imbalance of dopamine levels in the brain.  Having sex helps restore dopamine levels.  My concubines, the Jenna Shea and September Carrino lookalikes, are going to help restore my dopamine levels following my Pleistocene beer and pot party.

Pleistocene Turkeys (Meleagris sp.)

Early European colonists reported seeing flocks of wild turkeys numbering in the hundreds.  Turkeys flock together in the fall when they concentrate in areas abundant with such favored foods as acorns and grapes.  The hens and their young stay in separate flocks from the adult toms because the latter will peck the juvenile toms to death on sight.  In late winter and early spring the adult toms battle each other for the right to mate with the hens, and these battles also can sometimes cause fatalities.  The champion turkeys get to mate with several hens.  By mid-spring the hens leave the toms and lay as many as 20 eggs in cleverly concealed spots that they cover with leaves.  J.J. Audubon wrote the hens “…separate themselves, in order to save the eggs from the male, who would break them all, for the purpose of protacting his sexual enjoyments.”  The hatchlings follow the mother around and grow quickly on a diet of insects, arthropods, small vertebrates, grass, and fruit; so that by mid-summer they’re capable of escaping predators more often than not.

Two tom turkeys (Meleagris gallopavo).  Turkeys were common across most of North America during the Pleistocene.  There also were two now extinct species of turkey restricted to the southwest and California.

The oscellated turkey (Meleagris gallopavo), the only other extant species of turkey besides the eastern turkeys pictured above.  It resembles a peacock.  Turkeys evolved from an ancient species of peacock that crossed the Bering landbridge 30 million years ago.

Today, there are only 2 species of turkeys–the eastern turkey (Meleagris gallopavo) which lives over a wide swath of varied habitats in North America, and the oscellated turkey (Meleagris oscellata) which is restricted to the Yucatan penninsula in Mexico.  During the Pleistocene there were 2 additional species of turkeys though they were much more localized in distribution than the eastern turkey.  The southwestern turkey (Meleagris crassipes) lived in Arizona and New Mexico.  The California turkey (Meleagris californicus) lived in southern California.  The California turkey left more fossils at the La Brea tar pits than any other species of bird other than the golden eagle.  Scientists believe the turkeys scratched the surface away from the top of tar seeps, and the weight of the birds caused them to become mired in the tar.  Turkeys can weigh up to 50 pounds.   As of 2006, 11,116 specimens from at least 791 individual turkeys had been found in the tar pits.  Golden eagles attacking prey stuck in the tar pits became entrapped in turn, explaining the abundance of golden eagle specimens here.  Turkeys were probably a common item in the diet of the eagles. 

Range map of the eastern turkey colored purple.  The yellow is the estimated range of the Pleistocene California turkey.  Eastern turkeys have been introduced to California and other areas of the arid west where in some areas they depend upon manmade water sources for survival.

Anatomical evidence suggests California turkeys evolved from eastern turkeys, probably after the 2 ancestral populations became geographically separated when the territory between them became desert.  Turkeys require trees for roosting and a daily water supply, so desert habitats are unsuitable for them.

The extinction of the California turkey and the southwestern turkey can be blamed on a combination of environmental and anthropogenic factors.  The extinctions coincide with a dry phase of climate that lasted for hundreds of years and began about 11,500 BP.  However, scientists noted the 2 species survived an even drier period that occurred ~38,000 BP.  The scientists authoring the below referenced study suggest California turkeys flocked around shrinking sources of water where they were completely rubbed out by paleoindians.  If not for man, these 2 extinct species of turkeys would likely still be extant.  Trees and bodies of water have always been abundant in eastern North America, explaining why eastern turkeys survived man’s onslaught, until Europeans raped the environment and almost drove them into extinction too before modern conservation practices saved them.

David Steadman, one of the world’s foremost experts on Cenozoic bird evolution, thinks turkeys share a common ancestry with the peacock based on anatomical similarities.  He believes a peacock-like fowl crossed the Bering landbridge ~30 million years ago, and all subsequent turkey species were descendent from this species.  A fossil species, Rhegimornis calbates, dating to the early Miocene, had anatomical characteristics intermediate between the turkey and the peacock.  Remains of Rhegimornis were found in Florida.  The modern turkey probably evolved by late in the Pliocene–~2.5 million years BP.   Fossils of Pleistocene-aged turkeys have been found in Georgia from Ladds and Kingston Saltpeter Cave.

Turkeys evolved from a peacock-like ancestor that crossed the Bering landbridge ~30 million years ago.

Reference:

Bochenski, Zbigniew; and Ken Campbell

“The extinct California turkey, Meleagris californicus, from Rancho La Brea: Comparative Osteology and Systematics”

Natural History Museum of California Publications 2006

The Vanishing Chinkapin (Castania pumila)

Photo from google images of chinkapin nuts in a burr.

The chinkapin, a shrubby relative of the American chestnut and not to be confused with the similarly named chinkapin oak (Quercus muhlenberger), used to be locally common, growing on the tops of rocky hills in the piedmont region of the southeast and in the undergrowth of open pine savannahs on the coastal plain.  The early explorer, John Lawson, reported the trees as so common that hogs fattened on the nuts.  He described the nuts as smaller, rounder, and sweeter than those of its relative, the chestnut.  Most sources state that it was the better tasting of the two.  William Bartram found chinkapin growing in association with chestnuts and chestnut oaks (Quercus prinus) on the tops of rocky piedmont hills, a forest type that contrasted with that of the surrounding area which was mostly an oak forest but in the valleys between the rocky hills a much richer forest of black walnut, beech, hackberry, tulip, and sycamore grew.  Moist creek bottoms and richer soils kept the latter area from burning, but the thin dry soils at the tops of rocky hills endured frequent fires.  Oak and chinkapin thrive in fire prone sites because they’re shade intolerant and need open areas to grow.

Most of the jobs I’ve had in the Augusta, Georgia area have taken me to just about every neighborhood in Richmond and Columbia Counties.  I used to survey lawns for Orkin Lawn Care, and I worked for many years as a route manager for the Augusta Chronicle. While working I, of course, took note of the vegetation (ecology has always held a great interest for me), and I’ve never seen a chinkapin.  Botanists warn the chinkapin is in decline for a number of reasons: fire suppression, chestnut blight, and suburban development.  Without fire, shade tolerant trees begin to dominate, and chinkapin can’t grow in the shade.  The chestnut blight completely destroyed the once common chestnut forests.  The chinkapin is also susceptible but is better able to survive because it is a shrub that resprouts and can produce a crop of nuts before it dies back again from the disease.  Still, the blight reduces overall nut production.

The chestnut blight was a disaster for the ecosystem.  Chestnuts and chinkapins were important sources of food for wildlife.  Now, trees such as tulip, which produce no mast, have replaced chestnuts.  They may be beautiful trees but animals can’t eat beauty.  I think the lack of chestnuts explains why I saw almost no wildlife on my trip to the Smoky Mountains National Park last summer (see my blog entry “Gatlinburg, Tennessee: Tale of a Tourist Trap Nightmare” which is I believe in the June 2010 archives).

The chinkapin has two interesting adaptations that help it survive as a species.  It germinates quickly in the fall.  The nut ripens from September to November, and they produce heavily–up to 1500 nuts per bush, beginning when they’re just six years old.  Squirrels disperse the species by burying the highly valued food, but the chinkapins foil the squirrels when they germinate immediately.  After they’ve become a seedling, the squirrel can’t utilize them.  Fall germination prevents animals from destroying the entire progeny, but by producing a nut with high food value, they motivate the squirrels to disperse them.  The other adaptive characteristic is its ability to resprout vigorously.  Fire may kill the main trunk, but chinkapin will resprout and form thickets.  Deer also find chinkapin a favored food and will browse down the main trunk, causing the shrub to resprout and create thickets.  Their thickets provide great cover and food for turkey and grouse.

Fossil evidence shows that turkey and grouse were quite common in upland Georgia during the Pleistocene–both left abundant specimens at Ladds and Kingston Saltpeter Cave in Bartow County.  Two studies of sediment cores in Georgia found that chestnut/chinkapin made up about 2%  of the pollen spectrum during the Pleistocene.  Both sites (Nodoroc and Grays Reef) date to about 30,000 BP.  Chinkapin surely was a common component of the open oak and pine savannahs so prevalent then.  Its ability to resprout and fall germinate is an ancient adaptation to survive fire and megafauna foraging.  The more such animals as mastodon, horse, llama, and deer browsed, the more this shrub would bounce back and form thickets ideal for bird life.

The Indians used to cook chinkapin and hickory nuts with their venison in well-rounded stews.  Chinkapins are a nice starchy substitute for bread or potatoes; hickory nuts provided a nice oily substitute for butter.  Chestnuts, unlike most other nuts, are primarily a carbohydrate based food, rather than a fatty form of sustenance.  They’re sweet and bready and act as a laxative.  I hate to buy expensive imported European chestnuts when I think how abundant and cheap American chestnuts and chinkapins used to be.

Pleistocene Bears of Southeastern North America

Nothing demonstrates wilderness more than a robust population of free roaming bears.  During the Pleistocene before people were around to kill them and destroy their habitat, there must have been tens of thousands of bears living within the boundaries of what today is Georgia.  It’s possible that 5 different species could have been found here in the same time span, though we can be more sure there were at least 3 sharing the same range.  Today, only 1 species of bear resides in Georgia–an estimated 5100 black bears still roam the mountains, the Okefenokee Swamp, the Altamaha and Ocmulgee river bottoms, and Houston County.  Occasional stragglers leave these last strongholds and raid urban dumpsters and suburban bird feeders, but these occurrences are rare.  One study of Georgia bears determined that suitable habitat can support 1 bear for every 3 square kilometers.  That means ideally, Pleistocene Georgia hosted a population of 30,000-40,000 bears.  (*Georgia is about 60,000 square miles. 1.86 square miles =3 square kilimeters.  Moreover, during stadials Georgia’s land mass increased by about 10,000 square miles due to the fall in sea level.)

Here’s a review of every known bear species that lived during the Pleistocene in southeastern North America.

Black bear–Ursus americanus

Photo from google images of a black bear in the Okefenokee Swamp.

Ursus abstruscus is the probable evolutionary ancestor of American and Asian black bears which once consisted of a geographically continuous population.  Glacial ice separated the two populations at the beginning of the Pleistocene, resulting in two different species.  Bjorn Kurten notes that Pleistocene black bears grew as large as modern day grizzlies.  I believe Pleistocene black bears were larger and fiercer than their modern day descendents because they had to survive confrontations with saber-tooths, giant panthers, jaguars, and packs of dire wolves.  Cavers and scientists discovered black bear fossils at Ladds and Kingston Saltpeter Cave in Bartow County, and the Isle of Hope Site in Chatham County.  They’re also commonly found in Florida fossil sites but only a few have been recorded from South Carolina.

Florida spectacled bear–Tremarctos floridanus

Photo of a spectacled bear, Tremarctos ornatus,  from google images.  This is the only living species from the once widespread short-faced bear family.  It is a close relative of the extinct Tremarctos floridanus.  Of course, scientists have no way of knowing whether Tremarctos floridanus was also spectacled, but they call it that anyway.

Now extinct, this was likely the second most common species of bear in southeastern North America during the Pleistocene.  Only 1 specimen has ever been recovered in Georgia (at Ladds), but its fossils have commonly been found in Florida and South Carolina.  It’s thought of as primarily a vegetarian, but a recent study of Pleistocene bears concluded that all were opportunistic omnivores that would eat anything they could obtain.  Tremarctos’s range in the late Wisconsinian Ice Age seems to have been restricted to the southeast.  During warm interglacials it expanded as far north as Kentucky.  It probably just lived in the coastal plain of Georgia and South Carolina as well as Florida during colder climatic stages.

Lesser short-faced bear–Arctodus pristinus

Photo of a fossil jaw bone of Arctodus pristinus from Additions to the Pleistocene Mammal Fossils of South Carolina, North Carolina, and Georgia by Albert Sanders.

Photo of fossil bear teeth from the above mentioned publication.

It’s unclear from the fossil record whether this species co-existed with its larger cousin, the giant short-faced bear, or was simply ancestral to it.  Its fossils have only been recovered from a few eastern sites in Florida, South Carolina, Maryland, and West Virginia.  Teeth attributed to this species overlap in size with those of Arctodus simus.  Florida fossils of this species, including those from Leisey Shell Pit, indicate this animal lived from the early to mid-Pleistocene (~1.8 million-300,000 BP), whereas giant short-faced bear fossils in Florida date to the late Pleistocene (~300,000-~11,000 BP).  However, fossils of the lesser short-faced bear were found in South Carolina sediments thought to date from the Sangamonian Interglacial (~132,000-~118,000 BP) which is also considered late Pleistocene.  These South Carolina specimens haven’t been radiometrically dated, so no one knows exactly how old they are.  Perhaps this species did survive as a relic species in some geographical locations until the megafauna extinction.  Arctodus pristinus is considered more of a general feeder; Tremarctos floridanus a more herbivorous species; Arctodus simus a more carnivorous bear.

Giant short-faced bear–Arctodus simus

Dan Reed’s photo-shopped reconstruction of a giant short-faced bear.   

The giant short-faced bear ranks up there with mammoths, mastodons, ground sloths, and saber-tooths as among one of the most spectacular creatures of this era.  Studies suggest it lived by aggressive scavenging.  It’s extremely acute sense of smell detected blood from a great distance.  Then, the beast would relentlessly trot toward the source of the appetizing odor, and its sheer size would intimidate the partially satiated carnivore that actually made the kill into surrendering the carcass.  Arctodus simus fossils are more common in western fossil sites, but a few have been discovered in the southeast, proving it did occur here, at least sporadically.  An Arctodus simus skeleton rested in the Fern Cave system in Jackson County, Alabama which borders northwestern Georgia, until it was discovered by cavers in 1970.  In addition a number of teeth from this species have recently been discovered in north Florida fossil sites, and some Arctodus simus material was also discovered in Virginia.

Grizzly bear–Ursus arctos

Photo of a grizzly bear and cub from google images.

Welsh cave in Kentucky yields grizzly bear fossils dating to about 12,000 BP.  This is the easternmost known occurrence of this species.  Grizzly bears roam hundreds of miles, so it’s likely if they lived in Kentucky then that they must have entered Tennessee.  But the lack of grizzly bear fossils in other southeastern states suggests they never penentrated the region in significant numbers.  Still, I believe a few irregular stragglers may have wandered into what’s now north Georgia.  It may be that the existence of 3 or 4 other species of bears prevented grizzly bears from colonizing much of the southeast during the Pleistocene, and then man arrived, creating another obstacle blocking their migration into the region.  Grizzly bears are a relatively recent addition to North America’s mammalian fauna, but they did live on the continent prior to the LGM, 30,000 years BP.  They’re the same species as the Eurasian and Alaskan brown bears.

If I could live in the Pleistocene (part 4).

For those unfamiliar with this blog, I occasionally fantasize living during the Pleistocene but with modern conveniences, such as an adobe house with woodstoves, solar heating, electricity, and a time tunnel that connects me to the modern world.

I’ve thought of a simple way to observe bears from my abode.  Connected to my Pleistocene house is a 5 story watchtower designed in the shape of a lighthouse in which I can view the surrounding landscape.  I would take a barbecue grill to the fifth story which has a canopy but an open window stretching for 360 degrees around.  There, I would grill meats.  The aroma should attract bears and other carnivores from miles around.  A bear could potentially climb up the side of a light-housed shaped building, so I would have to have some kind of designed guards that would prevent this. 

I would avoid hunting bears, if possible.  I think modern hunters who kill bears are jerks.  I can understand why the pioneers did it.  They didn’t have grocery stores and had to eat and make use of what they could obtain.  But there is no reason to hunt bears today, unless they prove a danger to tourists.  They don’t reproduce as rapidly as deer, and it’s just not ecologically necessary to hunt them.

Bears were a valuable source of meat and fat for early settlers.  Early accounts reveal an important dish of the Indians.  The Indians frequently diced up venison (which is very lean) and fried it in bear fat.  Bear fat was also the number one source of cooking fat in New Orleans in 1800.  It was gradually replaced by lard as the settlers brought in hogs.

 

Tamias aristus, the Extinct Kicked-up Version of the Eastern Chipmunk

Ladds Mountain, located in northwestern Georgia, is perhaps one of the best Pleistocene fossil sites in the state and yields the most mammalian species of any, though not many are of the famous large species.  Many caves and fissures pockmarked the mountain.  During their existence, these caves afforded dens for the animal life of the time, but eventually they collapsed and eroded.  Fortunately for fascinated scientists, the calcareous flowstone mixed with red clay to preserve the fossils.

I took this photo of Ladds Mountain, Bartow County, Georgia.  A fence prevents honest people like me from trespassing to hunt for fossils.

The numerous fossils of small species found here provides intriguing clues about the paleoenvironmental conditions at the time they lived.

One of the interesting small species was the giant or noblest chipmunk (Tamis aristus).  Its anatomical characteristics were exactly the same as those of the living eastern chipmunk (Tamias straiatus) with the exception of a notable size difference–the extinct species was 10%-30% larger.

Skull comparison between the two species of chipmunks from a paper written by Clayton Ray.  Tamias aristus was larger but otherwise they’re similar.  I also notice a suture on top of the skull of the larger species that doesn’t appear on the specimen of the smaller species.

Photo of an eastern chipmunk from google images.  I chose this one because it shows the species in its favored habitat–in a rocky woodlot.  Chipmunks store food in cheek pouches and carry it to tunnels under boulders and tree roots where they hoard the food.  They become dormant during bad weather.  I believe this is why they survived the Ice Age while its larger cousin did not.  During the last interglacial it co-existed with its larger cousin.

Clayton Ray first studied the fossil remains of the giant chipmunk in the 1960’s.  He tentatively decided that it was a distinct extinct species, though he believed it may have merely been a larger subspecies of the still extant eastern chipmunk.  Today, the eastern chipmunk reaches its southernmost range limit in central Georgia.  They live around Atlanta and Athens but are absent in Augusta.  There are more rocky boulders and crevices in the piedmont than there are in the coastal plain. Chipmunks like to tunnel and den in and around big rocks.  The coastal plain is also a tad warmer, allowing chipmunk-eating snakes to be active for a longer time period of the year.  I consider these two factors to be the reasons chipmunk ranges are limited in the south to the piedmont and mountain regions.

Tamias aristus is not common in the fossil record, though that doesn’t necessarily mean it wasn’t successful and abundant for a time.  Fossil specimens have only been recovered from one site other than Ladds–Arredondo IIA, located in north central Florida.  Fossils from Arredondo IIA are thought to be Sangamonian in age.  The Sangamonian was a warm interglacial period lasting from ~132,000-~118,000 years BP.  No good radiometric dates from any of the fossils found at Ladds have ever been recorded, indicating the fossils were too old for carbon dating (carbon dating isn’t possible for fossils older than 50,000 years).  As far as I know uranium series dating and pottasium-argon dating have never been attempted or aren’t possible here.  However, fossil specimens of the extinct giant tortoise (Hesperotestudo crassicutata) and the Florida red-bellied turtle (which today only occurs in Florida) were recovered from Ladds–evidence that the fossils accumulated here during a period of time when the climate was much warmer than that of today.  This also fits Ladds in with a Sangamonian interglacial age along with Arredondo IIA.

Conversely, a few species found at the site indicate cooler climate as well, but it’s not a convincing list–none are definitively dependent on a cooler climate–and it’s unclear whether fossils of different ages are mixed here.  The late Dr. Alan Holman, North America’s foremost authority on Pleistocene reptiles and amphibians, studied the cold blooded vertebrates found at Ladds, and he determined the all lived here during the same phase of climate.  In my opinion  based on the preponderance of temperate and warm weather species, the Ladds fauna is probably from a full blown interglacial period.

Dr. Alroy tackled the problem of determining the age of fossil sites hampered by the lack of quality radiometric dating.  Using the known ages of species appearances and disappearances in the fossil record as a kind of index, he estimates the ages of sites.  He calls this “appearance event ordination” or AEO.  This method is necessarily a very rough and inexact estimate.  Nevertheless, he estimated the age of the fossils found at Ladds to be about 300,000 years old.  One of the species he uses as an index for Ladds is the Vero tapir.  He placed the Vero tapir as existing until 300,000 years BP, but I believe he made a mistake.  Bjorn Kurten considered the Vero tapir to be the common southeastern species of tapir until the megafauna extinction of ~12,500 years BP.  Moving the disappearance date of the Vero tapir changes the estimated date of Ladds fossils.  I have no way of knowing for sure, of course, but because the species of fossils here are so similar to those at Arredondo IIA, I suspect it’s also Sangamonian in age.  I’m more certain that the animals here did live during an interglacial of some kind, if not the Sangamonian, than the Yarmouthian (~200,000 BP) or the Aftonian (~300,000).

Tamias aristus  apparently co-existed with Tamias striatus because the fossils of both are found at Ladds.  They obviously share a common ancestry, probably evolving from the same species.  I hypothesize that their ancestor evolved along two lines:  the larger species grew bigger because it foraged year round, while the smaller species became dormant during bad weather.   Both species did well in the rich oak and chestnut forests of the interglacial age and perhaps well into the early Wisconsinian Age when the climate was still mild.  But as the climate became drier and cooler, grassland replaced forests.  The remaining forested areas provided limited habitat, and the smaller chipmunk adapted better.  I believe the smaller chipmunk had a survival advantage because it became dormant during the bad weather of the Ice Age.  The larger chipmunk could function year round–an advantage in a warm climate.  But it lost that advantage during the Ice Age and instead became victim more frequently to hungry predators in winter, while its smaller cousin stayed hidden and safe during times of the year when food became scarce for carnivores.

Here’s the list of mammalian species found at Ladds and Arredondo IIA.  Notice the striking similarities.  Note: there were other species living near these sites that never perchance left fossil evidence at either one. 

* denotes species found at both sites.  X denotes extinct species.

Mammalian species found at Ladds

*opposum

masked shrew

smoky shrew

*short tailed shrew

*eastern mole

little brown bat (cf)

gray myotis

eastern pipistrelle

big brown bat

*X Jefferson’s ground sloth (probably)–Ray refers to it as species indetermined

*X beautiful armadillo

* New England cottontail–I think it a rather dubious feat to be able to determine subspecies based on a few fossil bones.  This may have been a large subspecies of interglacial rabbit that grew this size due to high quality foraging in a rich forest

*X Noblest chipmunk

Eastern chipmunk

woodchuck

beaver

* rice rat

deer mouse

white footed mouse

X unnamed extinct species of mouse in the Peromyscus genus

* cotton rat

*woodrat

*Florida muskrat

muskrat

southern bog lemming

meadow jumping mouse

*X dire wolf (probably)–Based on one tooth, Clayton Ray considered it to compare favorably to the gray wolf.  Dr. Nowak, the foremost authority on Pleistocene canids, later looked at this tooth, and wrote that it did fall within the size range of dire wolf.  Because Ladds probably dates to the Sangamonian interglacial, it must belong to a dire wolf because gray wolves didn’t colonize North America yet.

*gray fox

black bear

X Florida spectacled bear

raccoon

fisher

* long tailed weasel (cf)

spotted skunk

striped skunk

hog-nosed skunk

river otter

* jaguar

cougar

* bobcat

X river cat–Scientists are unsure whether this was a distinct extinct species, a margay, or a jaguarundi. 

*X Vero tapir

horse

*X long nosed peccary

*X flat-headed peccary

* white tailed deer

X at least one species of unidentified ungulate, the teeth were in too bad a condition to determine the species

5 species of birds left fossils here too, including turkey, black duck, ruffed grouse, passenger pigeon, and a perching song bird

Dr. Holman recoded 22 species of reptiles and amphibians

Mammalian species found at Arredondo IIA

*Opposum

*X Jefferson’s ground sloth

*X beautiful armadillo

* short-tailed shrew

* eastern mole

least shrew

northern yellow bat

southeastern myotis

X Pleistocene vampire bat

eastern pocket gopher

southeastern pocket gopher

southern flying squirrel

*X noblest chipmunk

gray squirrel

*Florida muskrat

Florida mouse

cotton mouse

old field mouse

woodland vole

meadow vole

X Florida bog lemming

harvest mouse

* cotton rat

* rice rat

* wood rat

golden mouse

* rabbit in the cottontail genus

* long tailed weasel

*dire wolf

*gray fox

* jaguar

* bobcat

*X Vero tapir

*X long-nosed peccary

*X flat-headed peccary

* white tailed deer

X upland bison–Bison antiquus

X long-necked llama

X big headed llama

The paleodatabase lists 15 amphibians but just one reptile as being recovered here.  I think this is incomplete.  I believe more reptiles than that were found here but just haven’t been listed on that source.  42 species of birds, including 3 extinct kinds were found here, but again, they’re not listed on the paleodatabase.

The predominant environment at both sites during the Sangamonian interglacial was probably a rich oak and chestnut hardwood forest interspersed with small prairies and dotted with swamps and marshes.

References

Holman, Alan

“The Herpetofauna of Ladds Quarry”

National Geographic Research 1 (3) 1985

Ray, Clayton

“Pleistocene Mammals from Ladds, Bartow County, Georgia

Bulletin of the Georgia Academy of Science 25 (3) 1968

The paleodatabase.

(I’m still trying to get my hands on a copy of Clayton Ray’s 1965 paper devoted exclusively to the extinct chipmunk.  If I do, I’ll write another entry with any new details I learn.)

 

Pleistocene Passenger Pigeon Populations

(Please forgive the excessive alliteration in the title.)

It’s hard to imagine the massive number of passenger pigeons (Ectopistes migratorius) that used to live in North America as recently as the mid to late 19th century.  For a description of their numbers, I’ve dug up an account J.J. Audubon gave in his Ornithological Biography.  Before I reprint this passage I want to comment on his writing style.  I enjoy his prose, but he does have a bad habit of writing in the passive voice, a style Stephen King in his book, On Writing, referred to as farting in an elevator.  Also, English was his second language because he was born in France.  Nevertheless, I think this makes for a fascinating description of a nature scene that no longer exists.

“The multitudes of wild pigeons in our woods are astonishing.  Indeed, after having viewed them so often, and under so many circumstances, I even now feel inclined to pause, and assure myself that what I am going to relate is fact.  Yet I have seen it all, and that too in the company of persons, who, like myself, were struck with amazement.

In the autumn of 1813, I left my house at Henderson, on the banks of the Ohio, on my way to Louisville.  In passing over the barrens a few miles beyond Hardensburgh, I observed the pigeons flying from north-east to south-west, in greater numbers than I thought I had ever seen them before, and feeling an inclination to count the flocks that might pass within the reach of my eye in one hour, I dismounted, seated myself on an eminence, and began to mark with my pencil, making a dot for every flock that passed.  In a short time finding the task which I had undertaken impractical, as the birds poured in countless multitudes, I rose, and counting the dots put down, found that 163 had been made in 21 minutes.  I traveled on, and still met more the farther I proceeded.  The air was literally filled with pigeons; the light of the noon-day was obscured as by an eclipse; the dung fell in spots, not unlike melting flakes of snow; and the continuing buzz of wings had a tendency to lull my senses to repose…

“It may not, perhaps, be out of place to attempt an estimate of the number of pigeons contained in one of those mighty flocks, and of the quantity of food consumed by its members.  The inquiry will tend to shew the astonishing bounty of the great Author of Nature in providing for the wants of his creatures.  Let us take a column of one mile in breadth, which is far below average size, and suppose it passing over us without interruption for three hours, at the rate mentioned above as one mile in a minute.  This will give us a parallelogram of 180 miles by 1,  covering 180 square miles.  Allowing two pigeons to the square yard, we have one billion, one hundred and fifteen million, one-hundred and thirty-six thousand pigeons in one flock.  As every pigeon daily consumed fully half a pint of food, the quantity necessary for supplying this vast multitude must be eight million seven hundred twelve thousand bushels per day.”

***********************************************************

Some archaeologists believe the massive population of passenger pigeons that colonists in North America reported from 1700-1870 was a temporary phenomenon.  Thomas Neuman has written at least two journal articles suggesting passenger pigeon populations exploded following the decimation of Indians after their first contact with European diseases such as smallpox, influenza, and measles.  Before this, Dr. Neuman believes this species was not particularly common.  Supposedly, when Indian populations were reduced, there was more forest mast available for birds because humans weren’t gathering the nuts and acorns they fed upon.  In his book 1491 Charles Mann discusses this theory and notes that archaeologists find few passenger pigeon bones at sites of large Indian settlements.

I disagree with this theory because it makes little sense for several reasons which I shall enumerate.

1. Passenger pigeons could not survive as a species unless they existed in extremely large populations.  The survival strategy of this species was to reproduce rapidly and roost and nest in enormous colonies so that they overwhelmed predation.  Predators ate many individuals, but there was a limit to how much their stomachs could hold.  If, as these archaeologists suggest, the passenger pigeon was just an occasional bird, the species would’ve become extinct long before the white man arrived on the continent because their defense mechanisms revolved around living in large colonies.

2. Even if human populations were at the high end of what archaeologists believe, they would’ve made little impact on the amount of forest mast available.  Pre-Columbian forests were extensive, and there was always plenty of forest mast for both humans and huge pigeon colonies.

3. Archaeologists don’t find many passenger pigeon bones in sites of large Indian settlements because Indians probably went to their roosting grounds and feasted on them there and simply didn’t bring the bones back to their villages.

4. Jacques Cartier, an early explorer, reported large pigeon colonies on Prince Edward Island in 1534…before Indian populations were reduced by disease.

5. Pigeon fossils are abundant in an early Holocene fossil site in Western Canada (Charlie Lake, British Columbia).  They are also a common fossil in late Pleistocene avifaunas including Bell Cave, Alabama, Cheek Bend Cave, Tennessee, and Ladds and Kingston Saltpeter Cave in Georgia.

At Ladds fossils of only 4 bird species were discovered.  Passenger pigeons were 1 of the 4.  This may be coincidence, but it’s believed that passenger pigeon biomass made up 25% of all bird populations in North America during the early part of the 19th century.  Many more species of birds were found in the deposit at Kingston Saltpeter Cave.  I compared the minimum number of individual passenger pigeon fossils from KSC to the total bird remains of all other species found there.  Ruffed grouse were the most common species, making up 30% of bird remains, but passenger pigeons made up 6%, despite being a highly migratory bird.  Assuming they spent 6 months of the year around KSC, that means at times, they may have made up to 12% of the bird population in the area.  If they stayed in the area around the cave for only 2 months of the year, they quite possibly made up 36% of the bird population at certain times of the year there.

I must mention, however, that estimating ancient bird populations based on the number of bird fossils found in cave deposits is a rather dubious method.  Nevertheless, habitat for passenger pigeons in southeastern North America during the Pleistocene must have been ideal for this species.

During colonial times this bird nested throughout the midwest, but spent September-February in southeastern states.  For much of the duration of the Wisconsin Ice Age, most of the area where they later nested was under glacial ice, so it’s likely their nesting areas shifted south.  They probably were year round residents everywhere south of the Laurentide ice sheet, except during nesting season when they nested in southern river bottomlands where beech and oak trees remained plentiful, even during cold arid climatic phases.

Today, beech trees are a rare relic in much of the southeast, but during certain climatic phases of the Wisconsin Ice Age, they were even a dominant tree on some lands, according to records of fossil pollen in Alabama, and South Carolina.  From 14,000-11,000 years BP beech was a common tree, while pine, which dominated southern forests during the LGM, temporarily declined drastically.  Beech is well adapted to pigeon and squirrel foraging because this tree spreads through sucker roots, and if animals eat the tree nuts, this species can still propagate.  Beech tree pollen is also present in the Nodoroc fossil site in central Georgia near Winder and at the Gray’s Reef site off Sapelo Island, which was above sea level 30,000 years ago.  The latter site yielded evidence of a forest consisting of a strange mixture of cool temperate and warm weather species of plants.  The south’s Ice Age ecosystem was a mixture of woodlands and grasslands, and it provided excellent habitat for passenger pigeons.  I think the expansion of southern beech tree forests, as the Ice Age waned, is evidence the population of pigeons may have spiked about 14,000 years BP, creating the nucleus that later colonized the midwest after the glacier melted and broadleaf trees re-established themselves there.

References.

Driver, J.C.; and K.A. Hobson

“A 10,500 year sequence of bird remains from the southern boreal forest region of western Canada”

Arctic 45 (2) 1992

Ellsworth, Joshua; and Brenda McComb

“Potential effects of Passenger Pigeon flocks on the structure and composition of pre-settlement forests of eastern North America”

Conservation Biology 17 (6) pp. 1548-1558 2003

Mann, Charles

1491

Knopf 2005

www.paleodb.org