The Pleistocene- Vertebrate Fossils from Mississippi Gravel Bars 

Dr. Nina L. Baghai-Riding

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

Extent of ice sheets during the coolest glacialperiod, Cutchins and Johnston, 2000).

• 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.

• 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

en.wikipedia.org

The world of the ice ages is much more familiar to us than any other geological time – Pleistocene epoch

Most spectacular components of the Pleistocene are large animal bones of mammals.

Age of the Cavemen, mammoths, and saber-toothed cats.

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.

Mammoths came across the Bering land bridge from Eurasia to North America at 1.9 Ma\

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

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

Other important large herbivores:– Equus - One-toed horses– Tapirs – found in forested parts of the

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

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.

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 FossilTreasures of Florida-com

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

The Lower Mississippi River region served as an important ecological resource for many land-dwelling and freshwater animals.

Grassland habitats and forests prevailed - dominant presence of large grazing animals (bison, mammoth, horse, and stag moose).

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

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.

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.

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 List of taxa contained in the “Looper Collection”“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

Cervaices scotti – Stag MooseEuarctos americanus – American Black

BearEquus complicates – Fossil HorseEquus sp.Mammut americanum – American

MastodonMammuthus primigenius – Mammoth Megalonyx jeffersonii – Giant Ground

SlothOdocoileus virginianus – Whitetail DeerPaleolama mirifica – LlamaPlatugonus compressus – Flat Headed

PeccaryTapirus haysii – TapirTapirus veroensisTrichechus manatus – Manateeunidentified large and small carnivores

Vertebrate elements in Vertebrate elements in the collectionthe collection

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)

About half of the horse elements are teeth.

No isolated teeth are known from the whitetail deer.

Only about a dozen bison teeth

• Complex palmate antlers

• Similar lifestyle to a modern moose• Preferred mires and other wetlands environments such as spruce parklands

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

Bootherium bombifrons - Woodland Musk Ox (note red dots on the map as to where specimens have been found).• Lived in woodlands and plains

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.

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/arctodus.html)

•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) .

Manatee – Unusual find

• 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.

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.

• 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.

Our world today is depleted of large mammals although they were abundant during most of the last 50 million years.

Future workFuture work

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.