In paleontology, there is something to be said for plants and animals that live fast, die young and leave good-looking corpses. Who wouldn’t want to find a complete dinosaur skeleton, trilobite, sea urchin or fossil flower?
But for ichnologists, scientists who study traces of organisms’ behavior such as burrows and footprints, it’s more important to leave a lasting impression.
In some ways, most people are natural ichnologists. When we see tracks on the ground or in the snow, we wonder what made them. Perhaps we notice a new hole in our yard and wonder what’s living there. And if we stick a finger in, will it bite us? This is what ichnology is all about.
Such traces are useful, especially where bones, shells and other body parts are not preserved. Trace fossils – such as dinosaur footprints, crab burrows, borings or even coprolites (fossil feces) – can tell a scientist a lot about what animals lived in the area and what they were doing. Tracks can be used to tell the weight and speed of an animal; burrows tell about how an animal lived underground; coprolites tell what an animal ate. And all of these tell us about animals’ behavior.
Here, the present really is the key to the past.
By carefully observing traces made by living organisms, ichnologists can extrapolate what happened in the past. For example, if an ichnologist finds a rock with many footprints of varying sizes, but similar shapes, and all of them point in the same direction, she or he would reasonably conclude that the animals that made these tracks were traveling in a herd or pack. Maybe there are smaller prints near larger prints, which would be evidence of an animal nurturing its young.
Have you ever seen a clam with a perfect little hole in it? This too is evidence of past behavior – most likely a drill hole from where a snail enjoyed a scrumptious clam dinner.
So even though scientists can’t directly observe what an extinct organism ate, an ichnologist can tell a lot about its diet by examining coprolites for bones, fish scales, squid beaks or other parts of meals.
Next time you’re outside, take a moment to look around for footprints, trails, burrows and feces. Think about what these might look like preserved as lasting impressions. Soon, you too may be on your way to discovering the joys and wonders of ichnology.
Patricia Weaver is an invertebrate paleontologist and is the collections manager for geology/paleontology at the North Carolina Museum of Natural Sciences. Anthony Martin is a professor in the Department of Environmental Sciences at Emory University, a research associate with the N.C. Museum of Natural Sciences and the author of “Dinosaurs Without Bones.”