by Alex Gugel , all rights reserved
![]() | Capitol ReefPaleontology |
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Capitol Reef National Park
National Park Service
U.S. Department of the Interior
Paleontology
Capitol Reef’s fossils capture the
eternal struggle between life and
death on our planet.
Life and Death
The last 3.5 billion years of Earth’s history
have been a relentless and dramatic
struggle of life and death. Life on Earth has
grown in both size and complexity from
its humble origins as microscopic singlecelled organisms to include everything
from plants to dinosaurs, and of course,
humans. However, this amazing explosion of
life has not been without great peril. Five major
mass extinction events have occurred in Earth’s
history, eliminating up to 96% of all species. It is
in this constant face of death that life has taken
hold on our planet.
Timeline of Life
Ga – billions of years ago
Ma – millions of years ago
4.6 billion years ago
541 million years ago
Present
Precambrian
Formation
of Earth
(4.6 Ga)
First appearance
of life
(3.5 Ga)
Oxygenproducing
bacteria
(3.0 Ga)
Land plants
(434 Ma)
Free
oxygen in
atmosphere
(2.5 Ga)
Reptiles
(305 Ma)
Cells with
nuclei
(2.0 Ga)
Multicellular
organisms
(1.2 Ga)
Dinosaurs
(225 Ma)
Paleozoic
Birds
(150 Ma)
Mesozoic
541 Ma
Ordovician-Silurian
mass extinction
(443 Ma)
What is a Fossil?
Mammals
(115 Ma)
Modern
First
hominin humans
(6.5 Ma) (0.2 Ma)
Cenozoic
0 Ma
Late Devonian
mass extinction
(359 Ma)
Permian
mass extinction
(252 Ma)
Triassic-Jurassic
mass extinction
(200 Ma)
Fossils preserve the record of life on
Earth. Fossils are the physical remains or
traces of organisms that were once alive.
Paleontologists study fossils in order to
better understand the history and evolution
of past life. Fossils provide a wealth of
information on ancient ecosystems and
past climates, which together provide an
indication of the effects of changing climate
on Earth’s life—knowledge that will be
critical to addressing concerns in the face of
current climate change.
Cretaceous -Tertiary Another
mass
mass extinction
extinction??
(66 Ma)
Fossils are exceedingly rare. Most organisms die
and decay without leaving behind any preserved
remains or traces. It is thought that less than
one bone in a billion becomes fossilized. For
an organism or trace to become fossilized,
very specific conditions must be met. Most
importantly, fossilization requires that the item
be buried rapidly for initial preservation. In the
case of physical remains, minerals dissolved in
groundwater can then slowly replace the original
bone or shell until it is turned into stone.
Past Life at Capitol Reef
The extraordinary rock record at Capitol Reef spans 200 million years of Earth’s past,
encompassing the entire Mesozoic Period (252-66 Ma)—the “Age of Reptiles.” The Mesozoic
was marked by the rapid diversification of life, highlighted by the rise of the dinosaurs. Many
of the fossils found at Capitol Reef reflect this prolific period, where life flourished under warm
climatic conditions.
Triassic Trackways
Some of the oldest and most extensive
reptile tracks in the western U.S. are found
at Capitol Reef within the Moenkopi
Formation. Tracks and swim traces of
two crocodile-like species, Chirotherium
and Rotodactylus, are found as sandstone
casts in mudstone layers. These trackways
indicate that these species lived in a marineinfluenced environment and provide an
incredible snapshot of a day in the life of a
reptile…225 million years in the past.
Plant Megafossils
Plant megafossils are exposed at many
localities within the Chinle Formation at
Capitol Reef. These large plant fossils—
preserved as impressions, petrifications, and
casts—contain representatives from most
major groups of vascular plants including
ferns, horsetails, and conifers. The types of
plant species found in the Chinle suggest
that 225 million years ago, Capitol Reef
was a land of rivers and swamps with a wet,
tropical climate. These conditions provided
a suitable environment for life forms that
would not survive in the currently arid
conditions of southern Utah.
Giant Stromatolites
Bizarre fossils known as stromatolites are
located within the desert-formed Navajo
Sandstone at Capitol Reef. Stromatolites
are layered structures formed by the
accumulation of cyanobacteria in stagnant
water. They are the oldest fossils on Earth,
some dating back over three billion years.
Cyanobacteria were the dominant life form
for more than two billion years, and are
thought to be primarily responsible for the
oxygenation of the atmosphere—helping
sustain life as we know it on our planet. At
Capitol Reef, the discovery of five-meterhigh stromatolites suggests that the Navajo
desert had large bodies of standing water,
challenging current assumptions that it was
entirely dusty and dry.
Oyster Reef
A dense oyster shell reef dominated by the
oysters Exogyra and Pycnodonte represents
yet another form of life from Capitol Reef’s
distant past. These 100-million-year-old
oysters reflect a time when a sea inundated
this area and created the brackish marine
conditions necessary to support this form
of life. The shells of these oysters were
ultimately concentrated in the beach deposit
preserved as the Dakota Sandstone.
An Irreplaceable Legacy
Fossils are irreplaceable, non-renewable
resources. Excavating, removing, damaging,
or otherwise defacing fossils or other
paleontological resources within the
park diminishes our legacy, and is strictly
prohibited by federal law and is punishable
by fine and/or imprisonment. If you are
EXPERIENCE YOUR AMERICA
fortunate enough to find a fossil in the park,
leave it untouched, take a photo, and share your
exciting discovery with a park ranger. Keeping
fossils where they are found will help preserve
their scientific, educational, and interpretive
value for present and future generations.
www.nps.gov/care
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