# Weigh a Dinosaur

Andrew Heckert

, Department of Geology, Appalachian State University

Author Profile### This activity has benefited from input from faculty educators beyond the author through a review and suggestion process.

This review took place as a part of a faculty professional development workshop where groups of faculty reviewed each others' activities and offered feedback and ideas for improvements. To learn more about the process On the Cutting Edge uses for activity review, see http://serc.carleton.edu/NAGTWorkshops/review.html.

This page first made public: Jul 1, 2009

#### Summary

Lab or small classroom activity where students use scale models (read: toy dinosaurs) to arrive at estimates of dinosaur body mass. Teaches scale, unit conversions, simple calculations, and, at higher levels, importance of "materials and methods."

## Context

#### Audience

I use this in an introductory-level historical geology class if the class is small enough and I have a 75-minute lecture spot. I can take over a laboratory on the Tuesday class before Thanksgiving (a frequently skipped class) and use this as a relatively fun way to involve students with dinosaurs during the Mesozoic portion of the class.

I also use a variety of this in an honors freshman dinosaurs seminar. In that class I make it more of a writing assignmentâ€”they have to provide a true laboratory "write-up" replete with "materials and methods" (what did the measure and how) and compare it to a published compendium of dinosaur body mass estimates, analyze their results, provide sources of error, and so on.

If time allows, it is useful to have students compare different models of the same dinosaur. It is relatively easy to acquire multiple version of common dinosaurs such as Triceratops, T. rex, Stegosaurus, and various sauropods.

I also use a variety of this in an honors freshman dinosaurs seminar. In that class I make it more of a writing assignmentâ€”they have to provide a true laboratory "write-up" replete with "materials and methods" (what did the measure and how) and compare it to a published compendium of dinosaur body mass estimates, analyze their results, provide sources of error, and so on.

If time allows, it is useful to have students compare different models of the same dinosaur. It is relatively easy to acquire multiple version of common dinosaurs such as Triceratops, T. rex, Stegosaurus, and various sauropods.

#### Skills and concepts that students must have mastered

Essentially, students need only to know how to perform basic conversions and perform simple mathematics. One would think any college freshman would have the requisite skills, but it can still be shocking how much "coaching" is required.

#### How the activity is situated in the course

This is a stand-alone exercise. In the introductory classes its a reward for attendance (exercise is worth 1% of course grade, cannot be made up, is pretty much an all or nothing experience). In the honors class I like to run it fairly early in the semester as it requires a modest amount of teamwork (limited sinks and measuring devices), allows students to pick their "favorite" dinosaur, and affords additional opportunities to interact with each other.

## Goals

#### Content/concepts goals for this activity

Unit conversions

Importance of careful measurement

Problem-solving

Importance of careful measurement

Problem-solving

#### Higher order thinking skills goals for this activity

Evaluation and analysis of measurements/technique

Develop an understanding that a lot of work can go into a simple observation such as "a tyrannosaur weighed 4-6 tons."

Develop an understanding that a lot of work can go into a simple observation such as "a tyrannosaur weighed 4-6 tons."

#### Other skills goals for this activity

At the higher level, I want students to begin to understand the importance of making careful observations, documenting their work to make it replicable, etc.

## Description of the activity/assignment

Students select dinosaurian models (toys) from a selection of Carnegie, Natural History Museum (London) and other manufacturers (Schleich, Safari, etc). Each student identifies their dinosaur, places it on a cladogram (provided) and determines when it lived. They then measure the dinosaur in three dimensions (length, width, height), compare one or more of these dimensions to "real" dimensions provided (usually the model says what the length was). Dividing "real" by "measured" yields a scale.

Students then determine how much water their model displaces. NOTE: Most textbooks show this happening with a beaker. Beakers are no where near accurate enough to use, and many dinosaurs dont fit in them anyway. You need either extremely large graduated cylinders (unlikely) or else large containers in a sink. What works best is to have students fill a container to overflowing (in the sink, obviously), then gently dunk their dinosaur, causing the vessel to overflow, then retrieve their dinosaur. THEN you can use a graduated cylinder to refill the container and measure the amount of water displaced.

Once students have a scale and a volume, the can cube the former and multiply it by the latter to yield an estimate of the volume of the actual dinosaur. Multiplying this by a density estimate provides an estimated mass. I have them bracket it by taking 0.9kg/L and 1.05kg/L for "light" and "heavy." Feathered theropods are even lighter---I have them use 0.8 g/L for the light estimate. They then record their result (I am trying to generate a spreadsheet of these measurements over the years) and compare it to a published estimate. I should probably base their grade on the ratio of their estimate to the "actual" (if light, reversed if heavy) but generally just try to "police" the work---if they are way off, they need to go back and find what arithmetic error led to the problem.

In the introductory classes this is a simple 1-sheet worksheet (front and back). For the honors students, they take the assignment home and write it up.

PS. I let the anthropology majors play with models of Pleistocene megafauna instead.

Students then determine how much water their model displaces. NOTE: Most textbooks show this happening with a beaker. Beakers are no where near accurate enough to use, and many dinosaurs dont fit in them anyway. You need either extremely large graduated cylinders (unlikely) or else large containers in a sink. What works best is to have students fill a container to overflowing (in the sink, obviously), then gently dunk their dinosaur, causing the vessel to overflow, then retrieve their dinosaur. THEN you can use a graduated cylinder to refill the container and measure the amount of water displaced.

Once students have a scale and a volume, the can cube the former and multiply it by the latter to yield an estimate of the volume of the actual dinosaur. Multiplying this by a density estimate provides an estimated mass. I have them bracket it by taking 0.9kg/L and 1.05kg/L for "light" and "heavy." Feathered theropods are even lighter---I have them use 0.8 g/L for the light estimate. They then record their result (I am trying to generate a spreadsheet of these measurements over the years) and compare it to a published estimate. I should probably base their grade on the ratio of their estimate to the "actual" (if light, reversed if heavy) but generally just try to "police" the work---if they are way off, they need to go back and find what arithmetic error led to the problem.

In the introductory classes this is a simple 1-sheet worksheet (front and back). For the honors students, they take the assignment home and write it up.

PS. I let the anthropology majors play with models of Pleistocene megafauna instead.

## Determining whether students have met the goals

For the introductory students, I simply monitor their work and make sure that they arrive at an estimate in the ballpark (and it needs to be a pretty big ballpark due to vagaries of different brands). For the honors students, this is a full-blown, graded activity wherein the report is graded based on both its content and the quality of the writing and analysis.

More information about assessment tools and techniques.## Download teaching materials and tips

**Activity Description/Assignment:****Instructors Notes:****Solution Set:**

## Other Materials

## Supporting references/URLs

An activity akin to this is listed in Lucas and, I believe, Martins dinosaur text books. An article by Peczkis (1994) is also very useful.

Lucas, S. G., 2004, Dinosaurs: The textbook: Boston, McGraw Hill, 280 p. (more recent versions available).

Martin, A. J., 2006, Introduction to the study of dinosaurs: Malden, Blackwell Publishing, 560 p.

Peczkis, J., 1994, Implications of body-mass estimates for dinosaurs: Journal of Vertebrate Paleontology, v. 14, no. 4, p. 520-533.

Lucas, S. G., 2004, Dinosaurs: The textbook: Boston, McGraw Hill, 280 p. (more recent versions available).

Martin, A. J., 2006, Introduction to the study of dinosaurs: Malden, Blackwell Publishing, 560 p.

Peczkis, J., 1994, Implications of body-mass estimates for dinosaurs: Journal of Vertebrate Paleontology, v. 14, no. 4, p. 520-533.