This lesson has students investigate the geographical distributions, habitats, and other features of modern crocodilians and SuperCroc (Sarcosuchus imperator). Students will consider the things we can learn about one species by studying the other. They will create Venn diagrams to compare and contrast one modern species with SuperCroc. They will conclude by writing paragraphs describing this comparison and explaining how each species helps us learn about the other.

Geography, life sciences

Standard 8: "The characteristics and spatial distribution of ecosystems on Earth's surface"

Three hours

• Computer with Internet access
• Blank Xpeditions outline maps of the world
• Poster or construction paper
• Drawing materials

Students will

• label maps to show the distributions of modern crocodilians and the location of the SuperCroc fossil discovery;
• describe the ways modern crocodilians have adapted to their ecoregions;
• read and answer questions about SuperCroc;
• create Venn diagrams comparing and contrasting SuperCroc with a modern crocodilian species; and
• write paragraphs describing what their Venn diagrams show and explaining how each species helps us to learn about the other.

Have students look at the crocodilian pictures at the Florida Museum of History's Crocodilian Species List. Explain that crocodilians are a group of animals that includes crocodiles, alligators, gharials, and caimans.

Give each student or pair of students a world outline map).

Have students look at the crocodilian distribution map and ask them to label on their own maps the areas where crocodilians live today. They should use different colors to represent different crocodilian species (i.e., crocodiles, alligators, gharials, and caimans). Also have them label the location of the SuperCroc fossil discovery (the red dot in northern Africa).

Have students go to the Wild World Terrestrial Ecoregions map and click on four different ecoregions located in the areas inhabited by crocodilians. Ask them to shade and label these four ecoregions on their maps.

Discuss as a class the questions "What are the primary characteristics of these ecoregions? What do they have in common?" Students should notice that these ecoregions are primarily in tropical and subtropical locations and tend to have ample freshwater systems (e.g., rivers).

Have students return to the online crocodilian distribution map and select one crocodile, one alligator, and one gharial. Have them click on the buttons for each animal and read about its habitat in the pop-up window. For each species, ask them to write answers to this question: "What characteristics make this animal particularly suited to its ecoregion?"

Discuss students' maps and answers to the above question. Ask them to explain why they think modern crocodilians are distributed primarily in the world's tropical and subtropical regions.

Tell the class that crocodilians are a very ancient group of animals. Show them pictures of SuperCroc, and explain that this extinct species shares a common ancestor with modern crocodilians. SuperCroc lived about 110 million years ago, and its fossils have been found in the Sahara in the African country of Niger. They should have already labeled this location on their maps.

Ask students to read the National Geographic News article, "SuperCroc" Fossil Found in Sahara. Then have them answer these questions (you may choose to read the article and answer the questions as a class):

• What do scientists believe SuperCroc ate? What evidence do they have for this belief? [They believe it ate fish, small dinosaurs, and turtles; evidence includes the size and shape of its snout and teeth.]
• What was the Sahara like when SuperCroc lived there? [This region contained broad rivers that stretched across lush plains; it was not a desert at that time.]
• What is the relationship between SuperCroc and modern crocodilians? [They share a common ancestor.]
• What did SuperCroc probably do with most of its time? Does this resemble modern crocodilian behavior? What evidence do scientists have for this behavior? [It probably spent most of its time underwater, scanning the river's edge for prey; this behavior is very similar to that of the gharial. Scientists have found that SuperCroc had eye sockets tilted upwards and a "bulla" similar to a gharial's.]

Discuss these questions as a class:

• What can we learn about SuperCroc by studying modern crocodilians?
• What can SuperCroc fossils teach us about modern crocodilians?

Ask each student or group of students to choose one modern crocodilian species to compare to SuperCroc. They should conduct research on the Internet and, optionally, in print resources to find out details on these aspects of each species: habitat, geographical distribution, diet, size, and behaviors.

Have students compile their research into poster-size Venn diagrams that show the similarities and differences between the two species. They should create their Venn diagrams on poster or construction paper and include text and images to highlight the comparisons they are making.

Have students continue their research to investigate the reasons crocodilians have survived so long while other types of animals, such as dinosaurs, have become extinct. Ask them to report on their findings.

Students can use this simple crocodilian "family tree" for reference.

Crocodilians—Natural History and Conservation
National Geographic: SuperCroc
National Geographic: Wild World