Fossils
I don’t have much of a voice
today, so you are going to
have to listen closely. Take
notes, you will need this for
your next test, hopefully
Thursday!
What are fossils?
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•
•
Fossils are the
petrified remains
of ancient objects.
Petrified – means
turned to stone.
Ancient – means
very, very old.
Kinds of fossils?
•
Fossils can be of
animals, plants, or
other objects.
Fossils, big or small….
Paleontology and You
Paleontology is the scientific study of the fossilized
remains of early life on Earth. The remains can be from
different types of life, such as…
• Animals
• Plants
• Bacteria
• Fungus
(Stromatolite)
Brought to you by the Corpus Christi Museum of Science and History
Paleontology and You
A Paleontologist is not the same as an Archeologist.
Studies
fossilized remains
of early life
Studies
prehistoric people
and their culture
What is a Fossil?
A fossil is any remains, traces, or imprints of life that has
been preserved at some time in the geologic past. Fossils
must be at least ten thousand years old. Only a very small
number of organisms get fossilized.
The three main types of fossils are…
1. body fossils
2. trace fossils
2. pseudofossils
(coprolite)
Body Fossils
1. Body Fossils are the actual body or body parts of an
organism that has been preserved. The two main types of body
fossils are (A) unaltered remains and (B) altered remains…
A. Unaltered remains of
fossils means that the
remains have gone through
little or no chemical or
physical change.
There are four main
types of unaltered
remains of fossils…
(gastropod)
Body Fossils
A. Unaltered remains
- Original skeletal material: this means that the hard parts of
the organism are preserved as the original material.
(Ammonite)
(gastropod)
Body Fossils
A. Unaltered remains
- Tar impregnation: tar pits are excellent areas to preserve life
as a fossil. La Brea tar pits in California is one of the most
famous areas because of the large number of preserved life
forms found in it.
(saber-toothed
cat skull)
Body Fossils
A. Unaltered remains
- Amber entombment: some trees make a sticky and
thick liquid called “pitch” or “resin.” Small animals such as
insects and spiders or plant seeds and spores can get
trapped in the pitch and become preserved. If this gets
buried it can become amber.
Body Fossils
A. Unaltered remains
- Refrigeration: doesn’t mean putting it in the fridge. Animals
can get trapped in cracks of ice sheets, called glaciers, and
freeze. Mammoths have been found frozen in ice.
(This mammoth died in ice 39,000 years ago)
Body Fossils
Let’s review the main types of unaltered remains of fossils…
Unaltered remains of fossils have gone through little or no
chemical or physical change. Fossils must also be at least
ten thousand years old.
The types of unaltered remains of fossils are…
- Original skeletal material
- Tar impregnation
- Amber Entombment
- Refrigeration
Body Fossils
B. Altered remains of fossils means that the organisms have
gone through chemical or physical change.
- Permineralization: means that the hard parts of bones,
shells and plants have microscopic (too small to see with
our eyes) holes in them. When these hard parts are buried,
water that has dissolved minerals in it can soak into the
hard parts and collect on them. Can you see the how well
the pine cone is preserved?
(dinosaur bone)
(fossil pine cone) (fossil pine cone cut in half)
Body Fossils
B. Altered remains
- Replacement: means that groundwater with dissolved
minerals in it can replace the hard parts of buried organisms
with minerals.
(ammonite)
(log)
Body Fossils
B. Altered remains
Stromatolites – a
calcareous mound built up
of layers of lime-secreting
cyanobacteria and trapped
sediment, found in
Precambrian rocks as the
earliest known fossils, and
still being formed in lagoons
in Australasia.
Body Fossils
B. Altered remains
- Recrystallization: means that there is a chemical change
of the atoms that make up the hard parts of the organism. In
this ammonite, the hard parts have been changed to
Calcite, a mineral.
Body Fossils
B. Altered remains
The soft parts of organisms might also get preserved.
- Carbonization: when the soft parts of organisms get
buried in sediment, they can get squeezed and preserved.
(fish)
(cockroach)
(leaf)
Body Fossils
Let’s review the four main types of altered remains of fossils…
Altered remains of fossils means that the organisms have
gone through chemical or physical change and must be at
least ten thousand years old.
The types of altered remains of fossils are…
- Permineralization
- Replacement
- Recrystallization
- Carbonization
Let’s review Body Fossils
They are the actual body or body parts of an organism that has
been fossilized.
1. Unaltered remains - fossils that have gone through little or no
chemical or physical change.
2. Altered remains - fossils that have gone through chemical or
physical change.
Now, we are going to talk about trace fossils.
Trace Fossils
2. Trace Fossils are not the actual body or body parts of life
that has been preserved. These fossils show how an organism
lived, how it moved, what its feet looked like, how it raised its
offspring (its children), what it ate and what its shape was.
There are five main types of trace fossils…
(gastropod cast)
Trace Fossils
2. Trace Fossils
- Mold: This isn’t the green fuzzy stuff that grows on old food.
In paleontology, a mold is the imprint that an organism makes
in the sediment as it is fossilized. When you push your finger
into clay, the hole you made is the mold.
(Mold of a fossil seed)
(gastropod mold)
This fossil seed
was found in
Nueces County.
Trace Fossils
2. Trace Fossils
- Cast: A cast is the same shape as the original organism. Not
all organisms will have these. Casts are formed when the
original parts are all dissolved away and the empty space is
filled with sediment or minerals. None of the original material
is in the cast.
(Cast of a fossil seed)
(gastropod cast)
Trace Fossils
2. Trace Fossils
- Burrows: These trace fossils show how an animal such as a
worm (an annelid) moved through the soft sediment.
This worm tube
trace fossil is
hollow (the hole
goes all the way
through it).
Trace Fossils
2. Trace Fossils
- Tracks: can show how an animal moved and what its
footprint looked like. These tracks can tell us a lot about the
animal that made them in the geologic past.
(trilobite)
(Dinosaur tracks)
Do you see the people?
(trilobite tracks)
Trace Fossils
2. Trace Fossils
Ok, now we’re going to talk about a fun trace fossil…
- Coprolite: This is fossilized poop, called dung. Don’t worry, it’s
ok to touch it because it has been turned to stone. Coprolite can
tell a lot about how an animal ate and what it hunted.
Let’s review Trace Fossils
Do you remember what trace fossils are?
They are not fossilized body or body parts. Trace fossils help
us find out what prehistoric life was like.
Do you remember what the five types of trace fossils are?
- Mold
- Cast
- Burrow
- Track
- Coprolite
Pseudofossils
Pseudofossils (meaning “fake fossils”) are not fossils at all
even though they may look like one. These fossils may look
like many different things such as small branches.
(fossilized raindrops
that hit soft sediment)
(dendrite made by a mineral)
Pseudofossils
•
Oolitic limestone
- limestone
consisting of a
mass of rounded
grains (ooliths)
made up of
concentric layers.
How is a fossil made?
Ok, now that we have talked about body fossils, trace fossils
and pseudofossils, let’s talk a little bit about how a fossil is
made. Only a small number of organisms get fossilized. This is
because they must be preserved under
special conditions.
In general, dead organisms that…
get buried in soft sediment quickly…
and have hard parts have a better chance to get preserved.
The soft parts of dead organisms that…
get buried in soft sediment with little or no oxygen help to
preserve those soft parts. Little or no oxygen means that
there will not be many bacteria to eat the soft parts.
Paleontology and You
Why should we study paleontology?
Paleontology helps us to find out what Earth was like in the
geologic past. Studying fossils helps us to find out the age of
.rocks. Paleontology also helped to prove that the continents
move and were all connected together into supercontinents.
It helps us to find out what animals, like dinosaurs, were like.