Fossil Ages: There and Back Again

Name: _____________________________

Introduction:

Fossils can be used to determine the age of rocks. Since paleontologists know the time period that certain species were alive, originally using relative dating and then using absolute radiometric dating, rocks containing those species had to form during that same time period. An assemblage of fossils from a rock layer can then be used to refine an age for that layer. Sometimes, a single fossil can yield a refined age. This kind of a fossil, an index fossil, is of a species that existed for a relatively short period of time and is often geographically widespread.

Activity:

Your wacky uncle, Uncle Harold, has built a time machine. After school, you decide to travel back in time with him to see some dinosaurs. He sets the chronometer (the gauge that controls what time you travel to) to 70 Million Years Ago, in the late Cretaceous Period. As the time machine powers up, a fuse blows and the chronometer malfunctions, sending you back in time with no idea of when. You arrive in an unknown time. While Uncle Harold fixes the chronometer to safely return the two of you to your own time, you wander around this strange place. You make sketches of the dinosaurs you see (wow you’re good!). Uncle Harold fixes the chronometer, sets it to the present time, and the two of you return to your own time. Once you return, you quickly realize that you dropped your MP3 player back in the past. Fortunately, you have your sketches. You take those sketches to your local, friendly paleontologist to get the dinosaurs identified, as well as receive the age ranges of their existence. Using your sketches and age ranges (on the next page), answer the following questions to figure out where in time you lost your MP3 player so Uncle Harold can take you back to get them.

1. Based on your sketches and age ranges, when did Stegosaurus live?

2. Stegosaurus’ age range is graphed on page three. Graph the age ranges of the rest of the dinosaurs you witnessed.

3. After you have graphed the age ranges, look at where they overlap. Use a ruler to draw the lower and upper boundaries of this overlapped range and shade it in.

4. Based on the overlap of your extinct organisms’ age ranges, what is the time range in which you can you find your MP3 player?

Dinosaur 1: Stegosaurus

Time Period: 164.7 to 99.6 Ma

Dinosaur 2: Edmontosaurus

Time Period: 145.5-65.5

Dinosaur 3: Allosaurus

Time Period: 164.7 to 145.5

Dinosaur 4: Diplodocus

Time Period: 155.7 to 145.5 Ma



5. Archaeopteryx is a dinosaur that represents the transition of a certain lineage of dinosaurs to birds. It’s picture and age range are below.

Dinosaur 5: Archaeopteryx

Time Period: 150.8 to 145.5 Ma

If you had spotted Archaeopteryx on your trip, would it refine your age range?

6. If you saw Archaeopteryx, would the other dinosaurs have been useful in narrowing the age range?

7. A fossil with as short an age range as Archaeopteryx could possibly be used as what kind of fossil?