I ask students to reflect upon how fossils are identified. They need to either write down 3 thoughts and share them with a partner. As I do this activity with smaller groups so that I can supervise the fossil extraction and have conversations with them as they engage in the activity, I have the students share out with the entire small group. Here is one girl sharing her ideas.
After students share their ideas about how fossils are identified, I tell the students that today they are going to go on a fossil dig! I use fossils I ordered online. The fossils arrive in a matrix of pebbles and some sand which gives the student the experience of digging. The pieces are very small so I also supply magnifying glasses and tweezers. Students sort their finds into piles on a plate. Once they are certain that the sand and pebbles contain no more fossils, they can relocate the fossils to another paper or plate and refine their sort. I make xerox copies of the key that comes with the fossil matrix kit. Student uses these sheets as a reference point though some of the pieces are so small it's not always easy to determine what they might have been a part of.
I watch out for their tendency to jump to erroneous conclusions. For example, a single rib from an ancient scallop shell may look like a fish vertebrae to an excited third grader. I support students in writing specific, accurate details. If they are uncertain about their identification, I guide them to make statements about what something might be instead of definitely saying they've identified it.
The Pliocene matrix from North Carolina has some megalodon teeth and I also order a fossil kit that contains Devonian mosasaur teeth from Morocco. I made certain that the students kept these two piles separate, as they represent very different time periods and as well as different geographic locations.
I ask students to write down their initial observations about the sorting process, using these questions as a focus. I found that my class was engaged in the sorting for the entire class period so I sent these reflection questions as homework. Here as an example of student work.
For students who are interested in learning more about the very successful mosasaur group, the megalodon is an extremely interesting example. This is an interesting mosasaur size comparison. Here is some additional information about the giant mosasaur. Finally, here is some information for the students about the adaptations that helped them be successful, which ties nicely into our overall study of how some animals adapt and survive, some do not, and how some adaptations are beneficial in some circumstances but detrimental in others.