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with Fossil Treasures
Fossil Beds National Monument, Harrison, Nebraska
Geology Field Notes:
Agate Fossil Beds National
Monument in Nebraska preserves a wealth of information about the
“Age of Mammals” including the animals that lived there, the
environment they inhabited, and how the climate has changed over
time. About 19 million years ago, the
area was covered with a savannah, somewhat like those of east Africa
today. Herds of grazing animals and their predators once roamed the
plains. To the west, the growing Rocky Mountains started to block
the warm moist air moving across the land. With time the plains
became cooler and drier, and droughts became increasingly common.
With less food and water, animals gathered at the remaining shallow
waterholes. At one of these waterholes, hundreds of animals died as
the water ran out. Their skeletons were preserved under layers of
sand, silt and ash carried by wind and streams when the waters later
returned. The Monument preserves the
remains of many different mammals, including numerous complete
skeletons. Over time, the plains have been uplifted, with rivers
such as the Niobrara River, cutting channels down through the soils
and rocks, exposing these ancient layers and the fossils within.
Example animals from Agate
Fossil Beds include:
was a rhinoceros with 2 horns, but smaller than pony, that once
moved across the plains in great herds.
Moropus was something
like a cross between a horse and a giraffe. It was 7 feet tall at
the shoulder, and heavily built. Its hooves had claws that might
have been used from digging roots and bulbs or for defense.
Dinohyus was also 7
feet at the shoulder. This ferocious pig had large tusks, a massive
head and long, slender legs.
small, only 2 feet tall, looking like delicate deer. They also
roamed the plains in large herds.
Badlands National Park,
Geology Field Notes:
About 34 million years ago, during the
Tertiary Period, the area that is now Badlands National Park was a
broad marshy plain crossed by sluggish streams flowing out of the
highlands of the new Rocky Mountains to the west. Ancestors
and ancient cousins to the rhinoceros, horse, pig, cat and others
roamed the plains. Countless animals lived and died on these
plains. Remains left intact were buried by periodic floods and
converted into fossils. Rocks laid down as sediments during the
Eocene and Oligocene epochs are now laid bare, constituting one of
the richest fossil beds known.
Big Bend National Park,
Geology Field Notes:
Paleontology in Big Bend National Park:
Dinosaurs, Pterosaurs and Crocodiles in Big Bend National Park:
Big Bend displays
dinosaur remains from the last 35 million years of the dinosaurs'
existence, continuing uninterrupted from the Age of Reptiles into
the Age of Mammals. The geologic layers help paleontologists learn
the story of earth’s history. The rocks chronicle times when the
area was part of a deep ocean trough (500 – 300 mya), which then
rose to become part of an ancient mountain system, which then eroded
for some 160 million years, until 135 mya when a warm shallow sea
(an extension of the current Gulf of Mexico) covered the area. The
sea retreated 100mya leaving lowlands where crocodiles and turtles
lived. Another period of uplift and erosion followed. Eventually
similar plains mammals to those seen in Agate Fossil Beds and
Badlands lived here. Ancient mountains and volcanoes, rivers and
seas have all written their history in the geology of the park.
Big Bend’s rocks are
important to the study of how the earth changed between the
Cretaceous and Tertiary periods – the time when massive extinctions
occurred. One theory is that a massive meteor hit the earth,
causing severe changes that the dinosaurs and other animals were
unable to adjust to. Big Bend is relatively close to the area of
the Yucatan where such a meteor might have hit the earth.
Bend includes fossils for the three major groups of ruling reptiles:
dinosaurs, crocodiles, and pterosaurs. Over 90 dinosaur species,
nearly 100 plant species, and more than two dozen fish, frogs,
salamanders, turtles, crocodiles, lizards, and even early mammals
have been discovered here, giving us one of the most complete
pictures of a prehistoric ecosystem known anywhere on earth. Fossil
remains include the jaw of a crocodile, Deinosuchus riograndensis¸
whose body was over 40 feet long, the wing bone of the largest
pterosaur ever discovered, Quetzalcoatlus northropi
with a wing-span approximately 35 feet long, and Mosasaurus,
a 30-foot long reptile that lived in the sea, the skull of the
triceratops-like Chasmosaurus the largest known skull of any
land animal, and vertebrae from an Alamosaurus, over 100 feet
long, as well as fossils of hadrosaurs, tyrannosaurs and others.
Dinosaur National Monument,
Utah and Colorado
Geology Field Notes:
Dinosaurs and Dinosaur National Monument:
About 160 mya the area that is now
Dinosaur National Monument was covered by ocean waters, the evidence
of which is still in the rocks today. Not until about the midpoint
of dinosaur history, about 145 million years ago, did a suitable
habitat develop here: a low-lying plain crossed by several large
rivers and many intermittent streams, where a variety of ferns,
cycads, clubmosses, and clumps of tall conifers grew. In at least
one spot, river floodwaters washed a great number of carcasses and
bones onto a sandbar. There, mixed with the remains of turtles,
crocodiles, and clams that lived in the river, the bones were
preserved in the sand.
Fossils from several
different dinosaur families have been found here. Sauropods were
herbivores (plant eaters) that walked on all fours with long necks
and tails; they were often huge. Apatosaurus (better known
as Brontosaurus) was 70 to 75 feet long and weight about 34
tons. The only known Apatosaurus skull was found here. Barosaurus
and Diplodocus were close relatives weighing in at 25 and 13
tons respectively. Camarasaurus was a much smaller cousin.
The most complete sauropod skeleton found anywhere was found here of
the Camarasaurus. Stegasaurus, another four-legged
vegetarian is the largest and most famous of the stegasaurs. A
juvenile was found here, about the size of a dog, although in
adulthood it would have weighted from 2 to 5 tons. The ornithopods
were two-legged plant eaters, of which a Dryosaurus and a
Camptosaurus have been found.
Three predatory dinosaurs
have been found, although their fossil remains are much less common
here. Allosaurus is considered to be the most dangerous
predator of the Late Jurassic period. Two skeletons and a near
perfect skull have been found. Ceratosaurus is thought to be
the only predatory dinosaur with a horn on its head. It also had a
row of small bony plates down the center of its back and tail.
Ceratosaurs may have hunted in packs to kill larger dinosaurs.
The small Ornithoestes name means bird robber and it weighed
only 200-300 pounds.
Florissant Fossil Beds
National Monument, Colorado
Geology Field Notes:
Fossils of Ancient Lake Florrisant:
The rich deposits discovered at Florissant Fossil
Beds give us an unusually detailed look at what life may have been
like in ancient North America during the close of the Eocene
Epoch, about 35 million years ago. This was approximately 30
million years after the age of dinosaurs and at least 33 million
years before the first humans appeared.
During that time, Lake Florissant stretched 15 miles through an
ancient forested valley. Lush ferns and shrubs thrived under a
towering forest of redwoods, cedars, pines, and a colorful mix of
maples, hickories, elms, and oaks. In this warm, humid climate,
thousands upon thousands of insects crawled, flew, and buzzed about.
Fish, mollusks, birds, and mammals inhabited the lake and its
Exploding volcanic eruptions showered the area with millions of
tons of ash, dust, and pumice. Caught in the cloud were insects,
leaves, and fish; anything that could not escape died. Many fell to
the lake bottom and were buried. These volcanic eruptions occurred
over and over for perhaps as many as 700,000 years. Each time,
fragments of life become trapped in a layer of volcanic sediments at
the bottom of the lake. Eventually these sediments became finely
layered shale and the buried plant and animal life became fossils.
Even tiny creatures as fragile as butterflies have been
preserved as fossils, including antennae, legs, hairs, and the
pattern of their wings. Massive petrified redwood stumps are
evidence that ancient plant life here had its giants, too.
Paleontologists have collected more than 60,000 specimens from this
park for museums and universities around the world.
Fossil Butte National
Geology Field Notes:
Three ancient great lakes existed in the region
of Wyoming, Utah, and Colorado 50 million years ago, one of which
was Fossil Lake. A flat-topped remnant of rock (a butte) stands
where the center of Fossil Lake once was and reveals a wealth of
fossils in the ancient lake sediments. Fossil Butte National
Monument preserves the butte and its invaluable record of the past.
The numbers and variety of
species found here is amazing: more than 20 kinds of fish, 100
varieties of insects, and an as yet uncounted number of plants.
Paleontologists, have unearthed thousands of specimens during the
past 100 years. Many billions more lie buried in the butte and
surrounding ridges protected and preserved for future
paleontologists to study. The fossils are remarkable for their
detail. Many of the fish, for example, retain not only their entire
skeletons, but their teeth, delicate scales, and skin as well. And
perhaps most fascinating of all is the story the fossils tell of an
ancient life and landscape.
The scene 50 million years ago, during the Eocene Epoch of the Cenozoic
Era, was quite different from that today.
Fossil Lake, 50 miles long and 20 miles
wide, was nestled among mountains in a lush green forest of palms,
figs, cypress, and other subtropical trees and shrubs. Willows,
beeches, oaks, maples, and ferns grew on the lower slopes, and on
the cool mountain sides was a spruce and fir forest. In and around
the warm waters of the lake, animal life was diverse and abundant. A
broad range of fish inhabited the tributaries, shallows, and deep
water of Fossil Lake during its unusually long life of more than 2
million years. Gars, paddlefish, bowfins, and stingrays, though they
may appear primitive to some, still survive today, as do herring,
perch, and mooneyes. The lakeshore was alive with crocodiles and
turtles; insects, dog-sized horses. Early primates inhabited the
land. Birds and bats mastered the air.
National Park, Texas
Guadalupe Mountains National Park includes one of
the finest examples of an ancient fossil reef, which formed about
250 million years ago. This was the time even before the dinosaurs,
when the earth’s diversify of life included amphibians, fishes, and
insects as well as algae and fungus. The supercontinent of Pangaea
had not yet broken apart. A vast ocean surrounded Pangaea with a
narrow inlet connecting it to tropical inland seas including the
Delaware Sea which was 150 miles long and 75 miles wide in what is
now New Mexico and Texas, along the western edge of Pangaea, near
the equator. During the late Permian Period, the Capitan Reef
developed near the border of the Delaware Sea and grew for several
million years until near the close of the Permian Period when the
Delaware Sea’s connection to the outer ocean closed off and the sea
slowly evaporated away over thousands of years.
The Delaware Sea supported a
rich diversity of Permian life. The reef sustained an abundance of
organisms, including algae and sponges. Inhabitants of the rocky sea
bottom were sea urchins, bivalve clams, and flower-like crinoids on
long, slender stems. There were trilobites, a now extinct class of
arthropods with segmented, three-lobed shells. Ammonoids and
nautiloids, ancient cephalopods related to squid and octopi,
propelled their chambered bodies through the sea in search of prey.
Deeper on the reef, large, clam-like brachiopods clustered together
clinging to the seafloor by a single fleshy muscle, called a
pedicle. Tiny bryozoans formed in colonies that resembled delicate,
Hagerman Fossil Beds
National Monument, Idaho
Geology Field Notes:
Paleontology and Critter Corner
Fossil Beds National Monument is internationally significant because
it protects the world's richest known fossil deposits from the late
Pliocene epoch. The plants and animals preserved here represent the
last glimpse of time before the Ice Age, and the earliest
appearances of modern plants and animals. The sediments span some
550,000 years, from 3.7 to 3.15 million years ago, revealing grassy
plains dotted with ponds and forests that received more than 20
inches of rain and snow each year, over twice what it is today.
Mastodons, sabre-tooth cats, beavers, muskrats, otters, camels,
antelope, deer, ground sloths, hyena-like dogs, and fish, frogs,
snakes, and waterfowl lived here. Scientists have found fossils
from more than 140 animal species of both vertebrates and
invertebrates. Eight species have not been found anywhere else, and
44 were found here first. The Hagerman Horse, Equus
simplicidens, a zebra-like ancestor of the modern horse gives
the park its name. Hagerman Fossil Beds is one of the few sites
that preserves the number and variety of fossil evidence needed to
study past climates and ancient ecosystems.
environmental change occurs, most plants and animals have three
options: adapt, migrate, or become extinct. The ancient ecosystem
represented by fossil plants and animals illustrates each response
as the region changed from a wetter grassland savanna to drier,
high-desert conditions similar to those still seen today. Hagerman's
beaver and muskrat and many birds adapted giving rise to
similar species that are still here today. Llamas migrated
to South America, while camels and horses traveled across the Bering
Land Bridge to Eurasia. Ground sloths became extinct, along
with mastodons and other large herbivores. With the disappearance of
their primary prey, sabre-tooth cats and hyena-like dogs also became
John Day Fossil Beds
National Monument, Kimberly, Oregon
Geology Field Notes:
The John Day River Valley
holds some of the richest fossil beds in the world, a record of
remarkable continuity during the Tertiary Period of the Cenozoic
Era, or the “Age of Mammals”. While fossil beds that span five
million years are rare, this valley records more than 40 million
years of the diverse plant and animal life that existed here from 45
million to 5 million years ago. It is a record of such continuity
and duration that scientists can test paleontological theories
against the fossil record. Fossil beds contain vestiges of the
actual soils, rivers, ponds, watering holes, mudslides, ashfalls,
floodplains, middens, trackways, prairies, and forests. Fossil
plants are generally more helpful than animals for understanding
ecosystems. The John Day paleontology staff is working to identify
the plant types over time and so they can reconstruct the ancient
ecosystems and climates of eastern Oregon.
climate here changed from warm and moist tropical and subtropical
forests into cooler, drier grasslands over the course of 40 million
years. The plant and animal life changed as well. The evolution of
mammals can be followed here from early browsers and scavengers to
dogs, cats, pigs, horses, camels, rhinos, and rodents. To these were
added bears, bear-dogs, weasels, and a species of early elephant.
Finally the latest formation includes horses, sloths, rhinos,
camels, peccaries, pronghorns, dogs, bears, looking more like what
we are familiar with today.
Petrified Forest National Park, Arizona
Geology field notes:
Trees to stone:
Triassic reptiles and dinosaurs:
During the Late Triassic
Period, (225 million years ago) the area of Arizona that is now
Petrified Forest National was located near the equator on the
southwestern edge of the landmass known as "Pangaea". This tropical
location resulted in a climate and environment very different from
today, a large lowland basin with numerous rivers and streams
flowing through. The lush landscape included coniferous trees up to
nine feet in diameter and towering almost two hundred feet tall.
Ferns, cycads and giant horsetails grew abundantly along the
waterways. Crocodile-like reptiles, giant fish-eating amphibians
and small dinosaurs inhabited the land and water. Petrified Forest
National Park is one of the world's greatest storehouses of
knowledge about life on earth when the "Age of the Dinosaurs" was
time, as trees died, some were deposited on the flood plain adjacent
to the rivers and others were buried in the stream channels. Most of
the trees decomposed and disappeared. But a few trees were
petrified, becoming the beautiful fossilized logs visible today.
Most of the fossilized logs are from a tree called Araucarioxylon
arizonicum. Two others, Woodworthia and Schilderia,
occur in small quantities in the northern part of the park. All 3
species are now extinct.
Fossils of many different
kinds of early dinosaurs have been found. Just a few are described
here. Chindesaurus was an early primitive dinosaur. It was
8 to 12 feet long from head to tail, with sharp, sickle-shaped teeth
indicating a meat diet. Lightly built with exceptionally long hind
legs, it may have been one of the fastest land-dwellers in this
area. This speed helped it overtake its prey. Placerias gigas,
a large, bulky plant-eating reptile weighing up to 2 tons. It had
strong but toothless jaws and probably lived on a diet of tough,
fibrous plants. Large tusks may have been used to dig up roots and
tubers for food. Smilosuchus gregorii may have reached 30
feet in length. They lived a crocodile-like life in the rivers and
lakes preying on fish and smaller animals. Bony plates protected the
body and tail.