The Pleistocene- Vertebrate Fossils
from Mississippi Gravel Bars
Dr. Nina L. Baghai-Riding
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The Pleistocene Epoch lasted from
about 1.65 million until 10,000 years
ago.
Much of northern North America was
covered by a large ice sheet.
Continental glaciers extended in
Illinois and northern Missouri
• More than 18 million square kilometers
of ice covered North America
• The center of the ice sheet was about 3
km (almost 2 miles) thick.
Extent of ice sheets during the coolest glacial
period, Cutchins and Johnston, 2000).
•
Sea-levels were much lower
• Great Lakes and Finger Lakes were
formed.
• In the southeastern United States there were
pine-hardwood forest similar to that of the
modern Great Lakes as well as oak forests,
prairies, and swamps.
Compare the various vegetational zones 18.000 years
ago to the present
The world of the ice ages is much more familiar to us
than any other geological time – Pleistocene epoch
en.wikipedia.org
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Most spectacular components of the
Pleistocene are large animal bones of
mammals.
 Age of the Cavemen, mammoths, and
saber-toothed cats.
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Mammoths were the dominate fauna
of the Irvingtonian.
 They grazed on grasslands and steppes
in the Arctic (Prothero, 2006).
 They had huge grinding molars that
could crush almost any vegetation.
 Their molars look like a shoe with
deep treads.
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Mammoths came across the Bering land
bridge from Eurasia to North America at
1.9 Ma\
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Three different species: Columbian Mammoth,
Woolly Mammoth, and Jefferson’s Mammoth
Bering Land Bridge in orange connected Alaska to
Siberia. This area is currently under water.
Mammoth localities - common in areas that were
covered by savannas, grasslands, or tundra during
the last Ice Age.
http://www.museum.state.il.us/exhibits/larson/mammuthus.html
About 50% of the new genera immigrated from South
America and 27% from Asia during the Irvingtonian-Great Animal Interchange (Cutchins and Johnston
2000).
Other mammals that first appeared ~ 1.9 ma
1. Sabertoothed cat (Smilodon)
2. hares (Lepus)
3. jaguars
4. shrub oxen (Euceratherium)
119 genera of Irvingtonian mammals (Savage
and Russell, 1983).
North America was known for the American
mastodons (Mammut americanum)
• Mastodon molar from Danny West collection - note
its simple molar with conical rounded cusps.
 Forest animals
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American mastodon was about 3 meters (10
feet) at the shoulder, with slightly curved
tusks,
 One tusk usually was longer than the other
indicating feeding and behavioral
preferences.
 Tusks were used to pry on bark and
branches and broke them into pieces.
 Preferred spruce forests
http://www.enchgallery.com/2dmurals/mural%20images/mastodon%20mural.jpg
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Other important large herbivores:
– Equus - One-toed horses
– Tapirs – found in forested parts of the
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landscape
Mylohyus - Long nosed peccary
Platygonus – flat skulled peccary
Seven species of camels and llamas
including Palaeolama
Variety of deer and elk
Pronghorns
Musk oxen - Soergilia
Preying on the herbivores were:
 Hyena
 Ursus - Black bear
 Arctodus – huge short-faced bear – the top
predator in North America and the largest
carnivore that ever lived.
 Smilodon – sabertoothed cat
 Canis dirus - Dire wolf - heavily built,
short-limbed predator
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Other animals during the Ice Age
– Lepus – hares
– Bats
– Squirrels
– Beavers – including the giant beaver
Castoroides ohioensis – about 2.5 m long
and weighed almost the size of a bear.
– Moles, hamsters, porcupines
Rancholabrean – 300,000 – 10,000 years
ago marks the climax of the Ice Age
Mammal assemblage in North America.
– Bison – came in during this time from
Eurasia
– Bison latifrons - huge bison that had horns
that spanned 2 m in width.
– Other Eurasian immigrants came in
including the musk oxen, moose, reindeer,
new rodents.
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Numerous large mammals occurred in the
Midwestern United States below the ice
sheet
 Date between 40,000 and 10,000 years ago
(the last Ice Age).
 Most of these animals no longer live in the
United States and are extinct.
 Sites older than 40,000 years old are less
common than younger sites.
• Giant tortoises and strange glyptodonts the
size of a car occurred in the underbrush.
Glyptodont – from Fossil
Treasures of Florida-com
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Giant ground sloths 4.5 m (15 ft) tall
reaching for leaves to eat. Weighed close to
5,000 lbs (2,267 kg).
 Four species inhabited the United States.
 They spent all of their time on the ground
 The shape of their hip bones indicates that
they could stand up on their hind legs.
This would allow them to reach high up
into trees for the best leaves and twigs.
Ground sloth had blunt teeth (Specimen from Danny
West collection).
Huge claws and powerful arms were used to break
and bend branches
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The Lower Mississippi River region served
as an important ecological resource for
many land-dwelling and freshwater animals.
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Grassland habitats and forests prevailed dominant presence of large grazing animals
(bison, mammoth, horse, and stag moose).
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Tapirs (cow-sized) could swim, wallow in
mud, and hide in dense vegetation.
Giant Ice Age Beaver
 Probably an excellent swimmer
 Huge version of the modern-day beaver.
 8 ft or 2.4 m long from its nose to the tip of
its tail
 Its teeth possibly were used to uproot water
plants instead of cutting down trees.
 Probably did not build dams
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The Lonnie Looper Ice Age fossil vertebrate
collection is being acquired by Delta State
University.
 This collection contains 545 well-preserved
cranial and post-cranial elements of various
land grazers, browsers, carnivores, and
estuarine animals that inhabited the Lower
Mississippi River Delta.
 18 different semi-permanent gravel bars
(collecting sites) bordering woodlands along
the Mississippi River throughout
northwestern Mississippi and southeastern
Arkansas.
• The collection was obtained over a 5-year period
(1990-1995).
• Specimens are all well- preserved and
documented as to site and location (river mile
markers and longitude and latitude).
• Productive localities are Catfish Point, Henrico
Dikes, and Montgomery Island in Desha Co., AR,
and Rosedale Gravel Bar, Bolivar Co, MS.
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Each specimen has a collector number
and date of collection.
There is no other collection that so
adequately represents the late
Pleistocene life from this region.
Some specimens represent rare
documentations of the existence of
various mammals in North America.
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Specimens appear not to have moved far
from their source.
– Limb and toe bones
– Jaws and Teeth (incisors, canines,
molars)
– Vertebrae, Horn Cores
List of taxa contained in the
“Looper Collection”
Fish
• unidentified species
Reptiles
• Caudochelys crassiscutata – Giant Land
Tortoise
• Turtles – fluvial species
Birds
•
unidentified species
Mammals
• Arctodus simus – Great Short Faced Bear
• Bison sp. – Ancient Bison
• Bootherium bombiforns – Musk Ox
• Castor canadensis – modern beaver
• Castoroides ohioensis – Giant Ice Age
Beaver
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Cervaices scotti – Stag Moose
Euarctos americanus – American Black
Bear
Equus complicates – Fossil Horse
Equus sp.
Mammut americanum – American
Mastodon
Mammuthus primigenius – Mammoth
Megalonyx jeffersonii – Giant Ground
Sloth
Odocoileus virginianus – Whitetail Deer
Paleolama mirifica – Llama
Platugonus compressus – Flat Headed
Peccary
Tapirus haysii – Tapir
Tapirus veroensis
Trichechus manatus – Manatee
unidentified large and small carnivores
Vertebrate elements in
the collection
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Herbivores are dominant and
carnivores are rare
 Dominant herbivores:
– Fossil bison (129)
– Whitetail Deer (126)
– Fossil Horse (115)
– American Mastodon (32)
– Giant Ground Sloth (23)
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About half of the horse elements are
teeth.
 No isolated teeth are known from
the whitetail deer.
 Only about a dozen bison teeth
Stag moose – the name implies that it is cross
between an elk and a moose. Actually it was a
large deer.
http://www.museum.state.il.us/exhibits/larson/cervalces.html
• Complex palmate antlers
• Similar lifestyle to a modern moose
• Preferred mires and other wetlands
environments such as spruce parklands
Bootherium bombifrons - Woodland Musk
Ox (note red dots on the map as to where
specimens have been found).
• Lived in woodlands and plains
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Carnivores/ predators
– Great Short-faced bear (1)
– Dire wolf (1)
– American Black Bear (1)
Dire wolf
- Had a larger head and bigger teeth than
any past or present member of the wolf
family
- Hunted in packs
- A crushed skull was found on the
Rosedale Gravel Bar.
Great Short-faced bear
- Regarded as the most powerful
predator in North America during the
Pleistocene.
- Stood 8-10 ft (2.4 – 3 m) tall on its
hind legs.
- Canine teeth were suited for
puncturing tough hide
- Large, jagged molars were exceptional
for gnawing, tearing, and slicing meat.
A lower jaw was found on ‘The Bar’ in Desha
Country, Arkansas.
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The Great short-faced bear was
believed to become 13,400 years ago
as the result of competition with
invading brown bears (including the
grizzly bear) that are also predatory in
nature.
Range of Great short-faced
(http://www.museum.state.il.us/exhibits/larson/arct
odus.html)
Manatee – Unusual find
•The manatee is believed to have migrated up the
Mississippi River.
• This is the second reported occurrence of
manatee from the interior of North America
during the Pleistocene (the other occurrence is
from the Ohio River drainage basin in Ohio) .
• A right radius-ulna of a manatee was found
on the Ludlow Bar, Phillips Co., AR near
Rena Lara, MS.
• Length of the ulna is 139 mm; the radius is
114 mm.
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Reasons for this diverse assemblage:
- During the Late Pleistocene there was a
wide land bridge between North and
South America and between Asia with
North America. These land bridges
existed for thousands of years.
- Tapirs, llamas and dire wolves that once
lived along riverbanks in North America
moved to Central and South America by
the end of the Pleistocene.
– Horses migrated to regions of Asia
seeking better grazing lands. Grasslands
in North America were being replaced by
forests or deserts by the end of the
Pleistocene.
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Why the demise of these large
animals
– Habitats disappeared – changes in food
source
– Human hunting
– Infectious disease
Why was gigantism so widespread
among Pleistocene mammals?
 Large body size is beneficial in cold
harsh climates - good at conserving
body heat
– Several species of mammoth were larger
than any modern elephant
– The giant ground sloth was 21 feet long
– Huge camels had necks as long as
giraffes
– American lion was 11 feet long – larger
than any living lion today.
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Our world today is depleted of large
mammals although they were
abundant during most of the last 50
million years.
Future work
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Look at distinctive features of the
bone elements (color, attached
sediments) and relate to a geologic
source
 Look at the distribution of bones along
the river and see if they are
widespread or if they are concentrated
in certain areas
 Determine if there is a correlation of
certain fossils with certain point bars.
 Determine if dredging of the river has
to do with the distribution of the bone
density.