How can geologists identify different types of ammonites?
A. by the times of fossilization
B. by the size of their gills
C. by what they ate at the time
D. by differences in their shells
Geologists can identify different types of ammonites primarily by examining differences in their shells. Ammonites are extinct marine mollusks that lived millions of years ago, and their fossilized shells provide crucial clues to their identification. Here's how geologists analyze ammonite shells to differentiate various types:
1. Shell characteristics: Geologists carefully examine the shape, size, and overall structure of the ammonite shells. Differences in shell coiling, the number of chambers, and the presence of specific features (such as ribs or spines) can help determine the species.
2. Suture patterns: Ammonites possess complex suture patterns where the internal walls of the shell chambers meet. These patterns can be unique to each species and provide valuable information for identification. Geologists study the intricacies of the sutures to distinguish between different types of ammonites.
3. Shell ornamentation: The surface of ammonite shells can exhibit various textures, patterns, and ornamentation. Geologists closely examine these characteristics, such as the presence of knobs, nodes, or other shell features, which can be distinctive for particular ammonite species.
4. Size and proportions: Although variations in size can exist within a species, overall dimensions and proportions of ammonite shells can often help geologists classify them into different groups or genera.
5. Geological context: Understanding the geological formation in which the ammonite fossils are found can also provide further information for identification. Certain ammonite species have specific geological ranges and associations, which can aid in narrowing down their classification.
To summarize, geologists identify different types of ammonites by analyzing features of their shells, including shape, size, coiling, suture patterns, shell ornamentation, and considering the geological context. By carefully examining these aspects, scientists can determine the species and better understand the ancient marine ecosystems in which ammonites thrived.