Avian and Non-Avian Dinosaur Limb Morphology
Summary
In this activity students explore the concept of morphospace by using morphology data on snails and bird/dinosaur limbs. After the activity students should be able to quantify morphological data, interpret ternary diagrams, and explain how evolution can be constrained or influenced by morphology.
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Context
Audience
I use this exercise in my 400-level paleobiology class.
Skills and concepts that students must have mastered
For the first part of the exercise students should be able to make and interpret plots and calculate ratios. For the second part of the exercise students should be able to run R at a basic level (i.e. follow directions to copy/paste and slightly modify code).
How the activity is situated in the course
This is a stand-alone exercise as part of my module on quantifying morphological change and its link to evolution. By this time we have talked about evolution and adaptive landscapes, which I call back to in this exercise.
Goals
Content/concepts goals for this activity
1. Students can quantify morphological differences in organisms
2. Students can create and interpret ternary diagrams
3. Students can explain how the evolution of dinosaurs to birds developed more morphological diversity
Higher order thinking skills goals for this activity
Students need to be able to interpret large datasets. The key is getting them to understand not only where certain organisms plot within the morphospace, but where they are not plotting.
Other skills goals for this activity
The activity will strengthen students' command with R.
Description and Teaching Materials
The lesson begins by reconstructing part of the theoretical morphospace from Raup, 1966, using fossil/modern snail shells. To get an intuitive sense of the parameters of whorl expansion and translation, use tape to set a Y and X axis on a table and have students place the actual shell on the table as a datapoint.
The second pardt of the exercise uses data from Gatesy and Middleton (1997) to plot differences in limb morphology on a ternary diagram in R. These data show that as dinosaurs transitioned from one lomomotor module to three in birds, the morphological diversity of the limbs increased. This link between evolution and morphology is one of the key ideas we try to explore in this exercise.
A detailed list of required materials and teachings steps are included in the 'Avian and Non-Avian Dinosaur Limb Morphology Lesson Plan' file.
The student worksheet with R code is included in 'Avian and Non-Avian Dinosaur Limb Morphology Worksheet'.
The dataset is included in the zip file, 'Dinosaur and Bird Data.zip' and contains 3 .csv files, one each for dinosaurs, birds, and mesozoic birds.
The Dinosaur and Bird Limb Sheet is a short exercise to help students understand what we are doing. Print 1 per student.
Avian and Non-Avian Dinosaur Limb Morphology Lesson Plan (Microsoft Word 2007 (.docx) bytes Jan25 23)
Avian and Non-Avian Dinosaur Limb Morphology Worksheet (Microsoft Word 2007 (.docx) 10kB Jan25 23)
Dinosaur and Bird Data.zip (Zip Archive 10kB Jan25 23)
Dinosaur and Bird Limb Sheet (Acrobat (PDF) 1016kB Jan25 23)
Teaching Notes and Tips
One of the tricks of this exercise is getting students to see how dinosaurs have a restricted morphospace compared to birds. Asking students to mentally draw a box around all the dinosaurs and then all the birds seems to get them to think this way.
At the end of the exercise students are given some time to explore details in the dataset. If they don't know what different bird groups are, I ask them to do some googling to learn more about those animals.
Assessment
The questions in the Avian and Non-Avian Dinosaur Limb Worksheet are graded for credit.
References and Resources
Gatesy, Stephen M., and Kevin M. Middleton. "Bipedalism, flight, and the evolution of theropod locomotor diversity." Journal of Vertebrate Paleontology 17, no. 2 (1997): 308-329.
Raup, David M. "Geometric analysis of shell coiling: general problems." Journal of paleontology (1966): 1178-1190.