Fig. 15.4: Shape of the landmasses as they appeared approximately 100 million years ago. Adapted from Czerkas and Czerkas.

Problem Description:

The image provided is a map showing the shape of landmasses approximately 100 million years ago, along with various pieces of evidence such as fossils, rock types, glacial deposits, and glacier movement directions. The task is to analyze the map and use the evidence provided to infer how these landmasses might have been connected or related in the past.

Solution Approach:

To solve this problem, we need to carefully examine the evidence provided on the map and use it to infer the possible connections between the landmasses. Here’s a step-by-step analysis:

#### Step 1: Understand the Evidence
The legend provides the following types of evidence:
1. Fossils: Indicate the presence of specific dinosaur species (e.g., sauropods, stegosaurs, lystrosaurus).
2. Rock Type: Indicates the age of rocks in millions of years.
3. Glacial Deposits: Show areas where glaciers were present.
4. Glacier Movement: Arrows indicate the direction of glacier movement.
5. Landmass Above/Below Sea Level: Indicates whether the land was above or below sea level.

#### Step 2: Analyze Fossil Evidence
- Sauropods: Found in South America (1) and Antarctica (10). This suggests a possible connection between these two landmasses.
- Stegosaurs: Found in Africa (3) and India (5). This suggests a possible connection between these two landmasses.
- Lystrosaurus: Found in Africa (3), India (5), and Antarctica (10). This strongly suggests that these three landmasses were once connected.

#### Step 3: Analyze Rock Type Evidence
- The age of rocks is marked as "400 million years" in several regions, including parts of Africa (3), India (5), and Antarctica (10). This uniformity in rock age supports the idea that these landmasses were part of a larger, contiguous landmass in the past.

#### Step 4: Analyze Glacial Evidence
- Similar Glacial Deposits: Marked in Greenland (4), North America (8), and Antarctica (10). This suggests that these regions were once part of a larger landmass experiencing similar glacial conditions.
- Glacier Movement Directions: Arrows show consistent patterns of glacier movement in Greenland (4) and Antarctica (10), further supporting their historical connection.

#### Step 5: Analyze Landmass Above/Below Sea Level
- The shading indicates which parts of the landmasses were above or below sea level. For example, parts of Africa (3), India (5), and Antarctica (10) are shown as being above sea level, suggesting they were connected as a single landmass.

#### Step 6: Synthesize the Evidence
- Fossils: The presence of identical fossil species (e.g., lystrosaurus) in Africa, India, and Antarctica strongly suggests that these landmasses were once part of a larger supercontinent.
- Rock Type: Uniform rock ages (400 million years) in Africa, India, and Antarctica reinforce the idea of a shared geological history.
- Glacial Evidence: Similar glacial deposits and consistent glacier movement directions in Greenland, North America, and Antarctica suggest a historical connection.
- Sea Level: The above-sea-level shading in Africa, India, and Antarctica indicates they were part of a single landmass.

Conclusion

Based on the evidence provided:
1. Africa, India, and Antarctica were likely part of a larger landmass due to shared fossils (lystrosaurus), uniform rock ages, and similar glacial deposits.
2. South America and Antarctica may have been connected due to the presence of sauropod fossils in both regions.
3. Greenland, North America, and Antarctica were likely connected based on similar glacial deposits and glacier movement directions.

This evidence collectively supports the theory of Pangaea, the supercontinent that existed around 100 million years ago, from which today's continents broke apart through the process of continental drift.

Final Answer

$$
\boxed{\text{The landmasses were part of a larger supercontinent, Pangaea, which later broke apart due to continental drift.}}
$$