Cutting Edge > Paleontology > Teaching Activities > Hands-on Activities for understanding Ammonite Sutures

Hands-on Activities for understanding Ammonite Sutures

Clint Cowan
Carleton College
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

This page first made public: Jun 4, 2009

This material was originally developed as part of the Carleton College Teaching Activity Collection
through its collaboration with the SERC Pedagogic Service.


This lab/project/topic starts with a hands-on activity that can be accomplished in one to two hours, depending on how you do it. It is designed to make students demonstrate they know (really) what sutures are in ammonites, and more broadly, the goal is to generally show that complex shapes can arise from simple physical conditions in a fairly mundane system (a Hele-Shaw cell).

Used this activity? Share your experiences and modifications



200-level Paleobiology course for undergraduates (geology, biology and non-majors)

Skills and concepts that students must have mastered


How the activity is situated in the course

Starts a 4 week assignment that culminates in an essay/group discussion.


Content/concepts goals for this activity

Understanding some basic concepts: natural selection, driven v. passive trends.

Higher order thinking skills goals for this activity

3-D reasoning, Critical Thinking

Other skills goals for this activity

Searching and using the primary literature, writing (argument construction)

Description of the activity/assignment

There is a lot of primary literature on the origin (and purpose) of complex sutures in ammonites. It is still hotly debated what (if any) benefit complex sutures may have imparted to ammonites. But to start this whole topic (which results in an essay on whether changes in sutures represent a passive or driven trend), I use a set of hands-on exercises that are fun and eye-opening: examining cross-sections through modern nautilus shells, making a play-doh model of an ammonite, and using a Hele-Shaw cell experiment to make complex dendritic shapes.

I have found over the years, that students (and my faculty colleagues, too) can easily point out sutures to me on the ammonite fossils in our collection, but they really don't know what they're pointing to (they honestly don't!). So, I split my students (I usually have around 30 in my 200-level Paleobiology course) into teams of three, and we do several things (I do this all in one 4-hour lab, but you could easily do these in separate periods). First, they get an ammonite fossil (always a sediment-filled specimen with the mother of pearl phragmacone at least mostly gone so some of the sutures are clearly visible), and a couple of modern nautilus shells cut in half (I purchase these online from, and some play-doh (little 2-oz different color tubs I get from Kmart). They have to determine, and then build a model (using play-doh), what they're looking at when they're looking at the ammonite fossils, in particular, the sutures (sans sediment). They are allowed to look stuff up online or in their text. Results are amazing. I've had many teams build a very nice ammonite (usually a tube of play-doh, representing just one chamber with two septal walls at either end of the tube) and then they use a pencil to sketch the sutures on the outside of the phragmacone! I tell them to rethink this and then they work on it more... It's really cool when they finally realize that to make a model of the fossil sutures that they're looking at, they need to peel off their play-doh phragmacone to reveal the sutures (which are just the 1D line at the end of a 2D septal plane) (although the actual 1D 2D thing gets interesting when we delve into the fractal nature of the sutures, see below). Also, the modern nautilus shells beautifully show the difference between growth lines and sutures/septa. So I augment my assessment of their understanding by literally having each student individually trace for me (with their finger) what the suture is on one of the nautilus shells, and what a growth line is (the supplier I use polishes off the periostracum to reveal the mother of pearl with obvious growth lines). I have also taken whole Nautilus shells and buffed off a part of the phragmacone to reveal the edge of the septal wall, which is the exact equivalent of a suture in an ammonite).
Then, we run a Hele-Shaw experiment to get viscous fingering (which resembles ammonite sutures). I borrowed this hele-shaw design from the Center for Polymer Studies at Boston University ( Exploring Patterns in Nature. It consists of a pair of ~10-inch square glass plates, one with a hole drilled in it (our Shop makes these for me from standard glass). The hole is a size that fits common plastic tubing (outside diameter) which in turn fits a standard small syringe inside the tubing. The experiment works like this: put a 3 to 5 inch long piece of plastic tube in the hole, but make sure it doesn't stick out the other side (not more than flush), and seal this with some sort of removable sealant; let the sealant stiffen, and clean both plates with windex. Then, on the solid plate, put two stacked thin-section cover slips (I use micro glass little slips) at the corners of the plate, then put the hole-plate with tube up, on top of the cover slips (the inside surfaces need to be very clean), then clip the two plates together with binder clips on each corner. This is a Hele-Shaw cell. Then, with the syringe, inject glycerol between the plates, careful not to put too much in that is squirts out the sides. Then take a syringe with food color in it (darker works better) and inject the food color between the plates. The food coloring injects through the glycerol already in the tube. A beautiful dendrite is created. Compare these with ammonite sutures.
You can take it from here. I then stop the exercise and introduce the essay assignment (see uploaded documents).

Determining whether students have met the goals

Since it culminates in an Essay, I don't grade the exercise part, just the 5 page essay.

More information about assessment tools and techniques.

Download teaching materials and tips

Other Materials

Supporting references/URLs

For the Hele-Shaw: Center for Polymer Studies at Boston University Exploring Patterns in Nature. There is a lot of primary literature on ammonite sutures. I also use Gould's book: Full House, and The natural history of Nautilus by P. Ward; Nautilus : the biology and paleobiology of a living fossil, by W.B. Saunders and N.H. Landman; and Ammonites by Neale Monks and Philip Palmer, 2002, Washington, D.C.: The Smithsonian Institution Press, 159 pp.

See more Teaching Activities »