There is something uniquely spectacular about trace fossils.
Trace fossils—or ichnofossils—are fossilized remnants of animal activity. They are echoes of animal life, many that are millions of years old, that we can see and touch, tantalizing clues into their behavior and environment.
These traces take a number of forms, including coprolites (feces), gastroliths (stones ingested to help digestion), burrows, nests, and footprints.
[image of dinosaur tracks, Colorado, courtesy of David Parsons and Getty Images]
Footprints are the focus of Dr. Martin Lockley’s work. Over 30 years of his fossilized track research now resides at the University of Colorado Boulder.
Dr. Karen Chin, another trace fossil specialist with decades of experience, is widely known for her work on coprolites.
[images of coprolite and display info from the Boston Museum of Science, taken by the author]
The work of these two scientists comes together in the exhibit “Steps in Stone,” now at the University of Colorado Museum of Natural History. Showcasing some of Dr. Lockley’s extensive collection, the exhibit is curated by Dr. Chin.
[image of exhibit entrance, courtesy of the CU Museum of Natural History]
Originally from the UK, Dr. Martin Lockley began teaching at the University of Colorado Denver in the 1980’s. He retired in 2010, but his research continues today.
“When he decided to retire from his professor position,” Dr. Chin explained in a phone interview, “he wanted his research collection to go to a place where it would be cared for in perpetuity and would still be available for people to study. And since the University of Colorado Boulder is a sister institution to the University of Colorado Denver, it made sense for the collection to come to us.”
An accompanying website, with text written by Allison Vitkus—one of Dr. Chin’s graduate students—Dr. Karen Chin and Dr. Martin Lockley, describes in more detail the type of tracks Dr. Lockley has collected and donated to the University.
“Because of Prof. Lockley’s efforts, the University of Colorado’s Fossil Tracks Collection is exceptional in having specimens that represent tremendous temporal, taxonomic, and geographic breadth. It includes around 3,000 original or replica specimens of footprints and trackways, as well as about 1,600 full-size acetate footprint and trackway tracings. These specimens come from over 20 countries on five continents (including 21 states within the USA).” – Allison Vitkus, Dr. Karen Chin
Moving such a collection from one university to another is not a small enterprise.
“Martin Lockley and I applied for and received an NSF (National Science Foundation) grant to help us transfer the tracks to our museum.”
Dr. Chin described the process of creating the current exhibit, a team effort of about 15 people from various departments within the Museum of Natural History.
“Allison and I had already been writing about different aspects of fossil track research. We sat down and asked, ‘what are the things that we think are the most fundamental and interesting concepts of fossil tracks that would be interesting for people to learn about?’ We then put together a list of things we wanted to write about and matched that with tracks in the collection.”
[image of Dr. Karen Chin and exhibit docents, courtesy of the CU Museum of Natural History]
“We decided we wanted people to think about the concept of ‘moving’ and to recognize that fossil tracks tell us about locomotion in the past. ”
In other words, it is not just a look backward in time; it encourages the visitor to think about movement in all forms today and the evolution of that movement over Earth’s history.
Consider, for example, how fish might make tracks: fins brush the ground while swimming in shallow water. Consider, too, the tracks animals make while running, walking, limping, or even swimming. The type of footprint remaining and the length between each step (or stroke) offers valuable insight to scientists. Insects, mammals, birds, pterosaurs, dinosaurs….all of these species have left their marks in stone, and all of them are represented in this exhibit.
To help highlight how different body structures affect the type of tracks an animal leaves, members of the museum’s educational department procured imitation animal tails that kids can wear. Kids are also encouraged to ‘Walk Like a Pterosaur!’ in which they can don representations of pterosaur forelimbs with wings.
“There’s a portion of the exhibit that’s called ‘Locomotion Without Legs,’ that reminds us that not all animals that leave tracks or traces have legs,” said Dr. Chin. “Modern snails and sea urchins and are good examples of this.”
“We discuss the oldest evidence that we know of for movement in the fossil record, which is about 565 million years. We don’t know what kind of animal made the trace. It may have been something like a sea urchin, but we just don’t know.”
“There are a certain number of deposits around the world that preserve weird impressions of animals from before the Cambrian,” she continued. “Actually, we don’t even know whether all of them were animals or plants! There are no modern analogues of these organisms because they went extinct.”
“One of the oldest deposits of this particular biota comes from Newfoundland. Researchers found an unusual trace in this deposits that extends for several inches. The trace appears to provide evidence of locomotion. This suggests that an animal had the capacity to move itself, which further suggests that it had muscles. This is a huge deal because the fossil trace is so old. I think this is very cool because we often take our ability to move for granted.”
This particular trace fossil was described by Dr. Alexander Liu, Dr. Duncan McIlroy, and Dr. Martin Brasier in 2010. How fascinating to think that something this small and from an organism that remains a mystery provides important evidence for movement when the Earth was still relatively young. (First evidence for locomotion in the Ediacaran biota from the 565 Ma Mistaken Point Formation, Newfoundland) The actual trace fossil is not part of the exhibit, but its image is available for visitors to see.
“We often automatically think that animals have the ability to move from point A to point B,” Dr. Chin mused. “But there are a number of very successful animals that live without relocating from one place to another, such as sponges and corals. So it is interesting to think about when animals first developed the ability to move. ”
Another example of the variety and importance of tracks are the Laetoli trackway: a set of prints from Tanzania. The exhibit displays a life-sized cast of the trackway, footprints from two hominin adults and a smaller set of footprints that might have been a child.
“Their footprints were preserved when they walked on recently deposited volcanic ash. These tracks are important because they provide some of the earliest evidence that our ancient relatives, the australopithecines, walked bipedally.”
“As Dr. Lockley has continued his research on tracks,” explained Dr. Chin, “he has often acquired replicas of fossil tracks from around the world. That is what is great about tracks: that you can make a lot of different casts of them.”
“It’s an intense process,” Dr. Chin stated, referring to the creation of an exhibit. “There are so many details. But I gained new appreciation for the great work that the exhibit designers and the museum education people do.”
In response to whether it was a positive experience, she said, “I did enjoy it!”
“Now, I have to say,” she laughed, “it’s a lot of work. I didn’t mind the work, it’s just that I’m also teaching and doing research, so it’s kind of hard to juggle doing all of that at the same time.”
“I think there are two larger points that I’d like people to take away from the exhibit.
“I want people to gain a sense of appreciation for the tremendous amount of research Dr. Lockley has done on fossil tracks all over the world.
“I also want people to appreciate the informative value of tracks and other trace fossils.”
[image of Dr. Karen Chin and docents, courtesy of the CU Museum of Natural History]
“At many times we tend to focus on body fossils: the bones of mammoths and the bones of dinosaurs, for example. They are very interesting, and they really fire up our imagination in considering what those ancient animals were like.
“But, I also want people to appreciate that trace fossils–which provide evidence organisms’ activity—also offer important information on the history of life.
“It’s very much akin to walking on a trail these days and looking for animal sign. You look for tracks and scat and scratches and toothmarks. And we do the same when we look for trace fossils in the fossil record. Tracks are just one exciting example of trace fossils.”
A Mammuthus columbi-sized THANK YOU to Dr. Karen Chin for her time, her fascinating insight and for generously helping me understand Ediacaran biota! It was a tremendous honor and pleasure for me to connect with her. An enormous thank you to Cathy Regan as well for providing wonderful images of the exhibit!
“Steps in Stone” is available through December 31, 2015: http://cumuseum.colorado.edu
If you are interested in learning more about trace fossils, Dr. Martin Lockley has written a number of books. Dinosaurs Without Bones by Dr. Anthony J. Martin was published this year, and this author highly recommends it!