Self-study
Shark teeth are among the most common vertebrate fossils; yet fossilized shark skeletons are much less common—indeed, comparatively rare among fossilized vertebrate skeletons.
"Surprising" Phenomenon
Why are fossils of sharks’ teeth so common while fossils of their skeletons are rare?
Objective
The right answer will be a hypothesis that explains a key difference between the teeth and skeletons of ancient sharks. That difference must result in fossilized teeth being more likely to be found, either because there are actually a higher number of fossilized teeth in the world or else because something makes it easier to discover those tooth fossils.
12.
Which one of the following, ██ █████ ████ █████ ██ ███████ ███ ████████ ███████ █████████ ██████
a
Unlike the bony █████████ ██ █████ ████████████ █████ █████████ ███ ████████ ██ ██████████ ███ █████ ███ ████ ███ ████ ████ ██████ ██ █████████ ████ █████████ ███
This explains a key difference between the teeth and skeletons of sharks. Shark skeletons, which are composed of cartilage, are much less likely to fossilize than shark teeth. Because of this, fossilized shark teeth are more likely to be found than fossilized shark skeletons.
b
The rare fossilized █████████ ██ ██████ ████ ███ █████ ███ █████ █████ ██ █████ █████ ████ █████ ██ █████ ███████ ██ █████ █████ ███ ██████████
This doesn’t explain the difference between shark teeth and shark skeletons or account for why fossilized shark skeletons are so rare. Fossilized shark skeletons and teeth may end up in different areas, but we still don’t know why fossilized shark teeth are more plentiful.
c
Fossils of sharks' █████ ███ █████ █████████ ██ ███████████ ████ ███████ ██ █████ █████ ██ ██████
The stimulus tells us that shark teeth fossils are common. We can’t assume that those fossils are misidentified just because it’s difficult to distinguish them from fossils of other teeth. Also, we still have no information about why fossilized shark skeletons are so rare.
d
Some species of ██████ █████ █████ ████ ███ ████ ████ ████ ██ █████ ██████ █████ ██████████
We can’t assume that something that applies to some shark species alive today also applies to those species that are now fossilized. Also, even if ancient sharks did lose lots of teeth, we still have no explanation for why fossilized shark skeletons are so much more rare.
e
The physical and ████████ █████████ ████████ ██ ███ █████████████ ██ ███████ █████ ███ ██ ██████ ██ █████ ████████ ██ ███ █████████████ ██ █████ ██████████
If the fossilization processes of shark teeth and skeletons are equally common, it seems that the fossils should be equally common as well. We need a key difference between the two, not a similarity, in order to explain why tooth fossils are more common than skeleton fossils.