Fossil Footprints and Fragments:

“Field Geology”Your geology class is on a field trip to a fossil bed in Alberta, Canada. While exploring the site, you discover a slab of rock covered with interesting impressions. Your instructor invites the class to make observations and inferences about the imprints…

The rock is revealed over three days as the impressions are cleaned and uncovered…

Day 1

Day 2

Day 3

Identification of the Footprints:

The fossil footprints used in this activity are those of the Albertosaurus and the Edmontosaurus. These two dinosaur species were contemporaries, and paleontologists have inferred that the herbivore, Edmontosaurus, was likely preyed upon by the carnivorous Albertosaurus.

How tracks are formed:

A. This diagram shows a true track, natural cast, undertracks, and track infillings as they might appear in rock strata.

B. Track Variations Related to Sediment Consistency.All the tracks shown were made by a single dinosaur stepping on substrates of different consistencies, with the firmer substrates at left and the softer ones on the right. Notice the absence of distinct pads in the deeper prints (at right). The right-most track suffers from "mud collapse" or "mud back-flow," where soft sediment slumps back into a track depression, distorting its shape.

C. Basic Trackway Measurements.Pace angles (also called step angles or pace angulations) may be calculated using trigonometry once pace and stride measurements are made. On a quadruped trackway, these measurements should be made for both rear and front prints. One should also measure individual print lengths, widths, depths, and digit dimensions and angles.

Some Common Dinosaur Tracks

• After the practice footprints, you need to analyze another set of footprints. It can be another “practice” or a “real” image. See below for examples: You can “construct” an image of some dinosaur footprints for someone else.

Your turn!