Finding the evidence in excrement.

Finding the evidence in excrement

There's just no pretty way to skirt the issue. James McAllister studies feces -- fossilized forms of fish feces, to be frank. "It's quite often ignored; people tend to laugh at you if you work on this," says the paleontologist from the University of Kansas in Lawrence. Yet, in spite of the traditional nose-turning attitude toward his subject, McAllister and others are focusing anew on excrement by showing how these remains can open a window into the past.

In his study, McAllister looked at fossil feces -- called coprolites -- and regurgitation pellets found in the Hamilton quarry in Greenwood County, Kans., which contains roughly 300-million-year-old rock. While characteristic swirl patterns on the coprolites indicate they came from some type of fish, the tiny fossils provide much more information about what was being eaten rather than what was doing the eating. The excretions contain material from two types of fish: acanthodians, which had several long, protruding spines; and palaeoniscoids, which lack external spines.

Analysis revealed that the acanthodians appeared in regurgitated material more often than the paleoniscoids, but the reverse was true for the coprolites. This makes sense, says McAllister, since fish would be more apt to spit up spiny prey and digest the softer catch. Also interesting are the results of a close study of the acanthodian scales within the excrement. While acanthodian specimens found in the quarry range from 54 to 410 millimeters long, the excretions contain only scales from acanthodians that would have measured between 80 and 165 mm long, indicating that both small and large acanthodians escaped predation -- at least from animals that left behind coprolites and regurgitation pellets.