TRACKS, DUNG, BITE MARKS AND BURROWS: IMPRECISION IN TERMINOLOGY AND A PAUCITY OF ICHNOTAXONOMY HINDERS THE DEVELOPMENT OF THE STUDY OF VERTEBRATE TRACE FOSSILS

Vertebrate ichnology has developed significantly in the past 25 years, but two issues hinder its progress: (1) continued use in the technical literature of imprecise, undefined, vernacular terms such as tracks, dung, bite mark and burrow; and (2) a paucity of ichnotaxonomy, which, if used, would foster more precise description and provide a framework for communication and analysis. The majority of published studies of vertebrate traces are of “tracks.” A long tradition of naming “tracks” dates back to the 1840s. Few have advocated an ethological approach to “track” ichnotaxonomy, as in invertebrate paleontology, so almost all consider “track” ichnotaxa to be proxies of biotaxa. This ichnotaxonomy has have proven utility in biochronology, biogeography and ichnofacies. However, the broader terminology applied to these traces is often imprecise and poorly defined (e.g., “tracks,” “footprints,” “trails,” “tail drags,” etc.). In contrast, a precise nomenclature for bromalites dates back to Buckland’s 1829 proposal of the term coprolite. Recently, we proposed a comprehensive scheme for these and related trace fossils. The most important terms are bromalite (trace fossils that represent food items that have entered the oral cavity or gastrointestinal tract and have been expelled or retained within them), consumolite (fossilized food material preserved in, or partially in, the body cavity), demalite (skeletal material preserved within the body cavity of an animal that does not pertain to it), and gignolite (trace fossils and body fossils related to reproduction). However, relatively few workers other than us have used a formal ichnotaxonomy for vertebrate bromalites. The reluctance to apply a binomial scheme to coprolites is principally based on the misconception that modern feces are not distinguishable, even though wildlife biologists routinely track the distribution of taxa based on their feces. “Bite marks,” “skin impressions” and “burrows” lack a precise terminology and have few described ichnotaxa. “Bite marks” are, after bromalites and “tracks,” the most common vertebrate ichnofossils and by far the least studied. These trace fossils will benefit from a more rigorous terminology and ichnotaxonomy so that they become as readily discussed and categorized as are footprints and bromalites.