Glossary

A **coprolite** is a fossilized piece of animal excrement, classified as a trace fossil (ichnofossil) rather than a body fossil. Coprolites preserve direct evidence of ancient animals' diets and digestive processes through inclusions such as bone fragments, scales, plant fibers, pollen, spores, phytoliths, and parasite eggs. Their mineralization is driven primarily by calcium phosphate, with carnivore coprolites preserving more readily than those of herbivores because digested bone provides an abundant internal source of phosphate that facilitates rapid hardening. As biological records, coprolites occupy a unique position in paleontology: they capture information about food webs, plant community composition, parasitology, digestive physiology, and ecosystem structure that is unavailable from skeletal remains alone. The term was coined by English geologist William Buckland, who read his defining paper before the Geological Society of London in 1829 (formally published in the Society's *Transactions* in 1835), after recognizing that convoluted masses found by fossil collector Mary Anning in Early Jurassic Lias formations at Lyme Regis, England, were the fossilized excrement of ichthyosaurs. Before Buckland's identification, these objects had been known as 'fossil fir cones' and 'bezoar stones.'

A trace fossil, also called an ichnofossil, is a sedimentary structure formed by the biological activity of an organism, preserving evidence of behavior rather than the organism's bodily remains. Trace fossils encompass a broad spectrum of biogenic structures including footprints, trackways, burrows, borings, coprolites (fossilized feces), gastroliths, resting impressions, grazing trails, and feeding structures. They are distinguished from body fossils in that they record what an organism did—its locomotion, dwelling, feeding, resting, or predatory behavior—rather than what it looked like. Because trace fossils reflect direct organism–substrate interactions, they are classified using a parallel taxonomic system (ichnotaxonomy) based on morphology rather than the biological identity of the trace-maker; a single ichnospecies can be produced by unrelated organisms exhibiting similar behavior, and conversely a single species may produce multiple ichnotaxa depending on its activity and the substrate. The study of trace fossils is called ichnology, which is divided into paleoichnology (the study of ancient traces) and neoichnology (the study of modern traces). Trace fossils are of considerable significance in paleontology, sedimentology, and stratigraphy: they provide direct evidence of ancient behavior and ecological conditions, serve as reliable paleoenvironmental indicators through the ichnofacies concept, and are widely applied in petroleum geology for reservoir characterization. The base of the Cambrian Period itself is formally defined by the first appearance of the trace fossil Treptichnus pedum, underscoring their stratigraphic importance.

A **trackway** is a series of at least three consecutive footprints (tracks) left on a sediment surface by a single moving animal. Classified as a type of trace fossil (ichnofossil), a trackway directly records the locomotor behavior of an animal at a specific moment in time, in contrast to body fossils, which preserve anatomical morphology. From trackways, ichnologists extract a suite of measurements including stride length, pace length, pace angulation, and trackway gauge, which enable inferences about locomotion speed, gait type (bipedal or quadrupedal), posture, and social behavior such as herding or predator-prey interactions. Because trackways form in situ at the precise location where an animal was active, they provide unparalleled evidence for paleoenvironmental and paleoecological reconstruction that skeletal remains—which may be transported far from the animal's living habitat—cannot offer.