The Fidelity of the Fossil Record: Using Preservational Characteristics of Fossils within an Assemblage to Interpret the Relative State of Spatial and Temporal Fidelity
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).
Skills and concepts that students must have mastered
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.
How the activity is situated in the course
Content/concepts goals for this activity
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.
Higher order thinking skills goals for this activity
- Making predictions followed by comparison of data against predictions.
- Analysis of data.
Other skills goals for this activity
- Results and interpretations are written up in a short paper or essay.
Description of the activity/assignment
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.
Determining whether students have met the goals
Teaching materials and tips
- Activity Description/Assignment:Assemblage Fidelity Exercise Description (Microsoft Word 23kB May28 09)
- Instructors Notes:Discussion Guide (Microsoft Word 35kB May28 09)
- Solution Set: