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Lines of Evidence
for Past Change

Stories from the fossil Record

2. Stories from a Single Fossil

Each team was given a tray of similar fossils. Teachers were given three minutes to make individual observations and interpretations on a single fossil. They were asked to consider the following questions:

  • What is it?
  • What has happened to the organism? What kinds of hypotheses can you make?
  • Did those changes take place before or after death?

Story #1

It appears to be a cross-section of some kind of branch - very strong growth rings are apparent. However, one side has been rotted or chewed so perhaps one part was lying in a damp environment - therefore one side was exposed or buried and the decomposition occurred after death.

Story #2

Teeth - small, fragile and very evenly worn rows. The teeth belonged to an herbivore.

The animal died and the teeth became mineralized.

Story #3

Two fish, but different preservation. One died and decayed - it looked sort of exploded. Perhaps it was lying on the sea floor surface and was scavenged. The other is well preserved and its scales are intact, thus it probably was buried quickly after death.

Story #4

Part of a scallop shell. Probably broken after death, but can't tell if it was broken before or after it was buried.

There were barnacles growing on it, but can't tell if the barnacle settled before or after the death of the scallop. However there is a second, smaller barnacle within the first one! So that had to happen after barnacle #1 had died (real estate take over).

Story #5

Four similar shells with horizontal and vertical ridges (may be indicative of age). One organism burrowed through the shell, creating a vertical hole. Others left tracings that are more worm-like in appearance. In one case, there appears to be come kind of calcium deposit as if the shell were reacting to invasion, therefore growth around the original scar. Therefore this had to happen before death. One shell has both sides intact therefore it must have been buried quickly and in-filled with sand.

Story #6

Leaves. There are layers of compound leaves underneath a single leaf, therefore sort of like leaf litter. It must have been a forest environment. Some leaves are still together - again, that means that they must have been buried quickly.

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