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Fossils!
In this lesson, we will study fossils. Where did they come from? How are
they made? What can we learn from them? How do we identify and
classify them? These are just some of the questions we will answer.
1) For an introductory background to fossils, check the Royal Ontario
Museum Web Site:
Royal Ontario Museum (http://www.rom.on.ca/quiz/fossil/)
Review this material with the group.
2) Show and discuss the sample fossils provided with the lab: These
samples were purchased from WARD's Natural Science Establishment,
Inc., Rochester NY. (Fossil Display Pack 50 E 0115) Most of the
definitions given below either are from the material provided with the
samples or were obtained from the Royal Tyrrel Museum Fossil
Encyclopedia at http://tyrell.magtech.ab.ca/encyclo/t.html.
a) Horn coral: coral found only in Paleozoic rocks and no longer exists
in our present oceans. This fossil is about 375 million years old.

) Bryozoan ("moss animals"): small aquatic animals. They average less
than 1 millimeter in length but live in large colonies that are as much
as 30 cm across. This is approximately 12 inches -- the length of a
standard ruler. Modern bryozoans are found in warm shallow seas,
where they grow attached to the sea floor.
c) Brachiopod ("lamp shells"): brachiopods are a common type of
shellfish found in marine rocks from early in the Cambrian period
onwards, and they have survived to the present today. They had two
shells and lived attached to the sea bottom. There are around 200
living species of brachiopod, and around 30,000 species of fossil
brachiopods. Brachiopods still exist today but are very rarely found
as seashells on the beach.

d) Gastropod ("snails"): This typical snail shell has a spirally coiled,
single-valved shell. These mollusks first appeared about 550 million
years ago, and exist today both on land and in water. This example is
about 100 million years old.
e) Trilobite ("three lobed"): Trilobites are arthropods related to the
modern horseshoe crab. They were especially abundant during the
Cambrian Period and became extinct during the end of the Permian
Period (225 million years ago). A trilobite molted its exoskeleton
periodically as it grew, so it is possible that one trilobite could
produce many fossil remains. From Doug DeRosear's Fossil
Collection (http://burlingtonia.miningco.com/library/bltrilobite.htm).

f) Shark tooth: This tooth is a fossil remnant of a shark, which lived
some 20 million years ago. Sharks have evolved nearly 350 million
years, and have changed little during this period.
g) Crinoid Stem ("sea lilies"): Crinoids live in groups. Complete
crinoids are rarely preserved as fossils since the plates that make up
the animals hard parts fall apart at death. These animals are abundant
and important from the Ordovician to the Tertiary. Most of them,
both fossil and living species, have long stalks that anchor them to the
bottom. Attached to the stalk is a cup in which the main body organs
lie. The mouth lies at the center and five or more arms channel food
towards the mouth.

h) Petrified Wood: Petrified wood is created in a similar process as the
animal fossils already seen. About 225 million years ago, trees in an
ancient forest fell down and were washed downstream into a
floodplain. Here they were buried by volcanic sand and silt
sometimes to a depth of 1100 feet. Over time, the wood was replaced
by silica that was carried by the water. What we see today is a 'rock'
that is the same shape and size as the original piece of wood. The
beautiful colors are caused by other minerals that are mixed with the
silica. For more information check out the Petrified Forest National
Park Web Site
(http://www.shannontech.com/ParkVision/PetForest/PetForest.html)

The Fossil Company Geological Time Line
(http://www.fossil-company.com/time_line/index.html)