How to look at dinosaur tracks

Apr 30, 2007

A new study appearing in the May issue of The Journal of Geology provides fascinating insight into the factors geologists must account for when examining dinosaur tracks. The authors studied a range of larger tracks from the family of dinosaurs that includes the T. Rex and the tridactyl, and provide a guide for interpreting the effects of many different types of erosion on these invaluable impressions.

“Well-preserved vertebrate tracks in the rock record can be an invaluable source of information about foot morphology, soft tissue distribution, and skin texture,” write Jesper Milàn (Geological Institute, University of Copenhagen) and David B. Loope (Department of Geosciences, University of Nebraska, Lincoln). “However, in most instances, the tracks are less than perfectly preserved, and sometimes they can be barely recognizable as tracks at all.”

With this in mind, Milàn and Loope sought to describe and categorize different levels of preservation. For example, dinosaur tracks may still exist as true tracks, that is, the original prints left in the ground by the dinosaur. True tracks preserve many of the anatomical details of the foot, such as number of digits and impressions of claws.

However, the true tracks may be filled with sediment or the original tracked surface may have eroded away. In the latter case, erosion may expose prominent layers of concentric circles extending from the former location of the true track. These “undertracks” reveal the squishing and displacement of sand when the heavy dinosaur took a step.

“The tracks and undertracks of large theropods found in the [Middle Jurassic] Entrada Sandstone at the studied locality come in a wide range of morphologies, mainly as a result of present-day erosion that has exposed the track-bearing surfaces at different depths,” the researchers explain. “[They] demonstrate that great care should be taken when describing fossil footprints that have been exposed to subaerial erosion, because the shape, dimensions, and general appearance of the footprint become seriously altered by erosion.”

Geologists also must account for whether the step was taken on a sloped surface or on a horizontal surface, and whether it was taken during dry season or wet season.

For example, estimating foot length from tracks can be inaccurate without these considerations – the more erosion that has occurred, the larger the apparent dimensions of the track. Applications of this apparently larger foot size derived from an undertrack may lead to calculations of higher estimated hip length, and, as the authors point out, may also lead to slower speed estimates.

Source: University of Chicago

Explore further: Exceptionally well preserved insect fossils from the Rhone Valley

add to favorites email to friend print save as pdf

Related Stories

The Isthmus of Panama: Out of the Deep Earth

Apr 01, 2014

As dates in geologic history go, the formation of the slender land bridge that joins South America and North America is a red-letter one. More than once over the past 100 million years, the two great landmasses ...

Seeking a pot of geological gold

Dec 16, 2011

Researchers are moving a step closer to solving one of the greatest murder mysteries of all time. It happened roughly 200 million years ago, marking the boundary between the Triassic and Jurassic periods, ...

Algeo tracks evidence of 'The Great Dying'

Oct 28, 2010

More than 251 million years ago, at the end of the Permian period, Earth almost became a lifeless planet. Around 90 percent of all living species disappeared then, in what scientists have called "The Great Dying."

Oldest known spider's web found in amber

Nov 02, 2009

(PhysOrg.com) -- Pieces of amber containing parts of a spider's web have been found in East Sussex and dated back to the Cretaceous period 140 million years ago, which makes it the oldest spider's web known.

Recommended for you

Study claims cave art made by Neanderthals

Sep 01, 2014

A series of lines scratched into rock in a cave near the southwestern tip of Europe could be proof that Neanderthals were more intelligent and creative than previously thought.

User comments : 0