Fossil Identification Lab

Purpose: To learn to use an key to identify fossils and to determine the Geologic period of time the fossil existed.

Data:

Make a data table to record the following information about the fossil samples below. Use the links to help complete the table.

Sample #	Description	Symmetry	Fossilization	Common Name	Scientific Name	Phyla	Geologic Period
1
2
3
4
5
6
7
8
9
10
11
12

Table 1- Identify the fossils found in the table using the key that follows.

Sample #	Fossil	Sample #	Fossil	Sample #	Fossil
1		5		9
2		6		10
3		7		11
4		8		12

Symmetry:

Mirror-image symmetry in organism morphology (form, i.e., size and shape) can be an important method for determining mode of life. Active organisms benefit from bilateral symmetry (having a single plane of symmetry) which produces streamlining and concentration of sensory organs in the preferred direction of travel. Radial symmetry (numerous symmetry planes about a single axis in two dimensions) is beneficial to organisms that are more passive (their enviroment approaches them from all directions); corals are examples radial organisms. Many echinoderms such as this starfish possess pentameral symmetry (having five symmetry planes). Most starfish are vagrant (mobile) but sluggish epifaunal carnivores; their numerous skeletal elements lead to a poor fossil record. Sponges and other encrusting organisms (encrusters grow on top of rocky ocean bottom, shelly organisms, slow moving nektonic organisms such as whales, and one another) are asymmetric (lacking symmetry planes).

Symmetry of Body Plans

•Radial: the organism is symmetrical around a central point. Examples: algal fruiting body, some types of coral

•Pentagonal: five-fold symmetry. Example: some echinoids

•Coiled: –coiled in vertical plane. Example: some gastropods –coiled in a horizontal plane. Example: some ammonites

•Bilateral –bivalves: plane of symmetry passes between the valves; each valve is a mirror image of the other valve. –brachiopod: plane of symmetry passes through the center of each valve; one-half of each valve is the mirror image of the other half.

Identification Key to main types of fossils.

Fossils displaying Radial or Pentagonal symmetry	Fossils displaying Bilateral symmetry	Asymmetric Fossils
Tapering, cylindrical or cone shaped: Coral	Coiled in a single plane divided by transverse partitions: Cephalopod	Without transverse internal partitions: Coiled, opening shell very large, shell has two valves: Pelecypod Tightly coiled, small opening, one valve: Gastropod
Disk-shaped or flattened dome: Echinoid	Coiled in a single plane without internal partitions: Gastropod	Coiled, but not in one plane: With internal partitions: Cephalopod Without internal partitions: Gastropod Solid spiral ridge around central axis (corkscrew): Byrozoa
Non-tapered segments with hole in middle: Crinoid Stem	Not coiled:Shells or valves similar to clams: Plane of symmetry parallel to hinge: Pelecypod Plane of symmetry at right angles to hinge: Pelecopod Equilateral valves - mirror image: Brachipod	Not coiled: Resembles a narrow saw blade: Graptolite Shell not symmetrical, like a clam or oyster: Pelecypod Branching, twig-like with minute pores: Bryozoa
Composed of many plates- bud shaped: Blastoid -cup shaped: Crinoid	Not coiled: Shells tapering, cylindrical or cone shaped Heart shaped, domed, radial star pattern: Echinoid Segmented - divided into 3 lobes: Trilobite Segmented - elongated, resembles shrimp: Crustacean	Fossils of altered hard parts: With wood material replaced by minerals; Petrified Wood Of bone material replaced by minerals: Dinosaur Bone Fossil excrement replaced with minerals: Coprolites Carbon film from decay of organic material: Leaf imprint Tooth material: Shark tooth

Conclusion: What are fossils? How do fossils form? How can you identify fossils? How can fossils be used to date specific Geologic Periods of time?