Abstract

The soil ecosystems of modern floodplains of North America, South America, the Caribbean, Africa, Europe, and western Asia are the habitat of a group of limbless, fossorial reptiles (Order Amphisbaenia). Although body fossils are relatively abundant in North American Paleocene and Neogene paleosols, no ichnofossils are attributed to these organisms, largely because the morphologies present in modern burrows have not been studied. Because ichnofossils tend to have a higher preservation potential than body fossils, knowledge of the architectural and surficial burrow morphologies of such burrowing vertebrates as amphisbaenians can lead to the knowledge of their true stratigraphic and geographic ranges.

The behavioral responses of a common South American amphisbaenian to variations in soil composition, moisture, and cohesion were studied in the laboratory so that the architectural and surficial morphology of their burrows could be tied to these environmental changes. Qualitative and quantitative models were designed to describe the morphology of the amphisbaenian burrows and then used to distinguish them from other floodplain burrowers, including skinks, scorpions, and crayfish. Amphisbaenians were found to produce unique two- and three-dimensional biogenic structures that could be both distinguished from those of other organisms and tied to specific environmental conditions. From these data, variations in the morphology of amphisbaenian ichnofossils can provide more accurate interpretations not only of the paleoecology, paleoenvironment, and paleoclimate of floodplain paleosols but also of rates of sedimentation.