Michael Savarese

Florida Gulf Coast University

The course in which this exercise is implemented is an upper-division, elective course for undergraduates majoring in Environmental Studies, Marine Science, and Biology (FGCU does not have a Geology Major) that is taught once every two years (titled: Geobiology). The course focuses on the applications of paleontological data to problems in those disciplines. It is applicable for any college-level audience enrolled in a course in paleontology or paleobiology.

No equipment or materials are needed other than a computer from which the PowerPoint files can be projected. For best learning, having the digital files on a number of laptops is ideal, allowing students to work in small groups. The exercise could also be assigned individually with the computer files distributed through the institution's Computer-based Learning Management System (e.g, Angel, Blackboard).

Students should have been introduced to the nature of the fossil record and the processes associated with fossil preservation. The exercise should reside near the end of a topical unit in taphonomy.

Taphonomic fidelity is a critical concept for the entire course curriculum. When each application of paleontological data is introduced (e.g., evolution, phylogeny, functional morphology, environmental reconstruction, etc.), students are reminded to question whether or not the fossil record is adequate for that application. Before any investigation using paleontological data should proceed, the adequacy (i.e., temporal and spatial fidelity) of the dataset must be evaluated for that specific research question. Students are also made aware of the contrast between the completeness and adequacy of the fossil record. Consequently, this exercise is critical for its conceptual foundation.

The activity is designed as a conceptual exercise that could span a series of 2 to 3 class meetings. Students are asked to make predictions for 3 competing hypotheses (the 3 assemblage types), then collect evidence from the digital images, and then present their interpretation in written or oral form. These 3 steps could be spread out through the coverage of taphonomy within the course.

1. To provide an appreciation of the importance and application of taphonomic data to interpreting depositional history and doing paleoenvironmental reconstruction.
2. To become acquainted with various aspects of biostratinomy and the assessment of preservational state while working with real fossils.

3. To distinguish the difference between the completeness and adequacy of the fossil record and to appreciate that adequacy is problem specific.
4. Exercise provides a quick, inquiry based exemplar of the scientific method as applied to taphonomy and paleoenvironmental reconstruction. The 3 assemblage types are posed as hypotheses; predictions about the preservational state expected for each are made; data (observations made from the digital images) are collected and compared against those predictions; the hypothesis test is concluded; and then a new speculative question (i.e., what mechanism caused this assemblage to form?) is generated in need of additional testing.
5. Students work collaboratively as small groups to share observations and predictions.

- Hypothesis generation and testing / testing of competing hypotheses.
- Making predictions followed by comparison of data against predictions.
- Analysis of data.

- Students make short oral presentations.
- Results and interpretations are written up in a short paper or essay.

This exercise introduces students to the concept of temporal and spatial fidelity, to the different types of fossil assemblages, and how the taphonomic characteristics of an assemblage can be used to assess the relative state of fidelity. The exercise is suitable when introducing the discipline of taphonomy, typically covered near the beginning of a course in paleontology or paleobiology.

Because most universities lack appropriate collections of fossils, particularly collections from assemblages with unusual states of preservation, this exercise provides digital images of fossils from a Middle Devonian obrution deposit (or smothered assemblage) found within thin bedded limestones of the Hamilton Group of western New York State.

Students are asked to make predictions concerning the relative states of preservation likely to be found in life assemblages (biocoenoses) and death assemblages (thanatocoenoses and taphocoenoses). A biocoenosis is an assemblage that contains virtually all of the species that existed when the community was alive. A thanatocoenosis is a death assemblage where all the fossils represented existed within the community, but not all community members are present as fossils (species are missing). Finally, a taphocoenosis is an assemblage where not all species present in the community are represented as fossils, and not all the fossil species within the assemblage lived in the community (i.e., there is temporal or spatial mixing). Students are then presented with a PowerPoint presentation of the Hamilton Group strata, the limestones possessing the unusual fossil assemblage, and finally images of fossils with their preservational characteristics highlighted. The slides are annotated to provide observational descriptions and not interpretations. The exercise works best with students working in small groups with each group supplied with a laptop containing the PowerPoint presentation. Finally, each group is asked to interpret the assemblage type represented (bio-, thanato-, or taphocoenosis) and present a cogent argument citing supportive preservational evidence. (Because the assemblage is created through obrution, the assemblage is correctly interpreted as a thanatocoenosis – the fossils present were found within the community with many individuals preserved in life position and with behaviors represented; not all species in the community, however, are preserved as fossils.)

If time allows, students could be asked to make predictions concerning the preservational characteristics expected for each assemblage type in advance of the exercise. (A table is attached that I use to help frame their predictions.) Their interpretation and evidential argument could be written up as a short essay. I've asked students to do this individually and other times as a collaborative writing assignment for the group.

Once the correct assemblage interpretation is revealed to the students, they could be asked to speculate about the mechanism leading to this style of preservation (i.e., recognizing it as an obrution deposit). A few figures are provided that are helpful in explaining obrution.

The following files are uploaded as supportive teaching materials:
1. Discussion Assemblage Types.doc: Notes to guide a discussion to acquire predictions for taphonomic characteristics for each assemblage type.
2. Fossil Assemblages Exercise.ppt: PowerPoint presentation that describes the unknown fossil assemblage.
3. Exercise Assemblage Fidelity Assignment.doc: The handout provided students describing the exercise.
4. Obrution Deposits.ppt: PowerPoint presentation explaining obrution deposits.

Student understanding can be assessed at three junctures. (1) The list of predictions that each group compiles can be evaluated. (2) Their observations and interpretations can be monitored while in group discussion. And (3) students can be asked to write up their interpretations to reflect their overall understanding and their appreciation of the scientific method. The exercise could be written as an essay or as a short scientific paper. This could be done as individuals or as groups.