A crab shell is buried in sediments. The sediments get pressed and squeezed into stone. Meanwhile, the crab shell gets washed away leaving a hollow space the shape of a crab shell. What kind of fossil is this?
What choices do you have from your text book/class notes?
Trace fossil
Trace fossil
Based on the description provided, the fossil you are referring to is known as a "trace fossil." Trace fossils are indirect evidence of an organism's existence, rather than the remains of the organism itself. In this particular case, the hollow space left behind by the crab shell is an example of a trace fossil called an "ichnofossil," specifically a "void cast" or "mold fossil."
To determine the type of fossil, paleontologists use the following steps:
1. Identify the process: In this case, the crab shell was buried in sediments that subsequently hardened into stone. This process is known as lithification.
2. Recognize the organism: A crab, or at least its shell, was involved in this process.
3. Understand the outcome: As the sediments were compressed and solidified, the crab shell got washed away, leaving a void space that retained the shape of the shell.
Combining these steps, we can identify the fossil as a trace fossil, specifically an ichnofossil in the form of a void cast or mold fossil.