Xenosmilus Author/Adaptor: Al Janulaw

Overview: In this lesson, students play the roles of paleontologists on a dig. They “unearth” a few fossils at a time and attempt to reconstruct the animal the fossils represent.

Lesson Concepts:

• Life forms of the past were in some ways very different from living forms of today, but in other ways very similar.
• Fossils provide concrete evidence of past life.
• Form is linked to function.
• Scientists pose, test, and revise hypotheses based on research outcomes.
• Science explains the natural world using evidence from the natural world.
• Science does not prove or conclude; science is always a work in progress.

Grade Span: 5–12

Materials:

• One envelope of fossils, cut from the Fossil Sheet (HTML or pdf), per group
• One Xenosmilus Worksheet (HTML) per student
• One Skeletal Resource Manual (HTML or pdf) per student

Advance Preparation:

— Cut up the Fossil Sheet and place one set of fossils in each envelope. Leave a bit of white paper around each fossil to facilitate cutting.
— Make one copy of the Xenosmilus Worksheet for each student.
— Reproduce and staple copies of the Skeletal Resource Manual.

Time: One class period

Grouping: Threes or fours

Teacher Background:

The “fossils” are based on Xenosmilus hodsonae, a two-meter-long cat that lived in what is now Florida, between 1.7 and 1.0 million years ago. Xenosmilus looked somewhat similar to the more familiar saber-toothed cat, Smilodon, found in the La Brea tar pits of Southern California. It had long canine teeth, a stout body, and very powerful front legs, which may have been specialized to prey on large animals.

Teacher Resources: A web search for Xenosmilus, Homotherium or Smilodon will yield abundant results.

Teaching Tips:

Student enthusiasm will largely hinge on your showpersonship. Assure them that they are working with replicas of real fossils and functioning the way paleontologists actually work.

If you would like to use this activity again in the future, make sure students put the fossils back in the envelopes after finishing.

The Xenosmilus Worksheet is suitable for 6–12 grade students. Teachers of younger children may want to assemble more appropriate debriefing questions, such as What do you think it was? and How can you tell?

Vocabulary: fossil, skeleton

Procedure:

1. Pass out the envelopes of fossils and the worksheets.
2. Tell the following story (which includes instructions in parentheses) to the class.
3. The script:

   You and your fellow paleontologists are on a fossil dig in Florida, during August of this year. You have had to wade through three miles of swamp carrying shovels, picks, and other digging equipment. Then you needed to go back to the road to lug your tents and other supplies to your campsite. The first evening you plan the dig. One person will shovel mud, another will look through the mud for fossils and the third person will keep watch for alligators.

   The next morning the team arises early and begins digging. After several hours of shoveling mud, swatting mosquitoes, and sweating, you get lucky. Very lucky. Your team discovers four fossils and returns to camp with them.

   Without looking in the envelope, randomly remove four fossils and lay them on the table. These are the cleaned-up fossils. Now that you are back in camp for the evening, arrange the fossils so they make as much sense as possible. Write on your worksheet what you think the animal might be.

   (Allow students time to manipulate the fossils, reflect and record their hypotheses. Request that students not observe the workings of the other groups.)

   The second morning your team arises even earlier, excited about the possibility of finding more interesting fossils. This day, however, your all-terrain vehicle gets stuck in the mud and you have to dig it out during a raging thunderstorm. Your team finally gets to the dig site by noon and, fighting the heat and wet, manages to unearth three more fossils. You return to camp exhausted.

   Again, without looking in the envelope, withdraw three fossils. Use the next few minutes to arrange the new fossils with the ones from yesterday. On your worksheets, record what you think the animals is now.

   (Allow a few minutes for this task.)

   The third morning dawns bright and beautiful with the sort of sunrise that only happens in Florida in the summer. Thrushes singing, cicadas buzzing. The team heads out to what must be its last day of digging this season. At the site, an American crocodile walks past, paying little attention to the strange animals that are grubbing about in the mud. After several hours of digging and mucking, the team discovers three more bones. This makes a total of ten in three days. The team, fills in its hole, carefully marks the location on the map, and returns to camp for the last time. During the final evening in camp the team assembles its ten fossils.

   Again, without looking in the envelope, withdraw three more fossils. Put them on the table with the others and see what you have. Record what you think it is now.

   Bright the next morning, the team packs up and returns to the Museum of Paleontology. Upon arriving at the Museum you learn that other teams have had successful expeditions this summer and would be glad to share their results.

   Walk around the room and see what others have done with their fossils. Discuss your results with them and ask about theirs. (Allow a few minutes for this.) Now, with this additional information, write what you think the fossil is.

   After exchanging ideas with other scientists, your team goes to the library and consults a Skeletal Resource Manual, which has drawings of skeletons of living animals.

   (Pass out the Skeletal Resource Manuals.)

   Look through the Skeletal Resource Manual. Compare your fossils with the skeletons in the book. Record your final idea of what you think your fossil is. Answer all the questions on your worksheet and return the fossils to their envelope.

4. Collect all fossil envelopes and Skeletal Resource Manuals.
5. Have each team share with the entire class what they decided the fossil is. Ask for the evidence that led to their final hypothesis.
6. Ask if there is a general consensus on what the animal might have been. If there is no clear, final answer, ask what they would like to do to pursue it.
7. Allow students to search the Internet, use trade books, visit the library, or research the mystery at home.

Extensions:

Use the excellent activity, The Great Fossil Find, found on the ENSI website. The ENSI version of this lesson is somewhat more challenging than the activity above and may leave students a bit unclear on the identity of the fossils—much the way scientists spend a great deal of their time.

Acknowledgements:

Adapted from The Great Fossil Find on the ENSI website: www.indiana.edu/~ensiweb/lessons/gr.fs.fd.html.