Down-to-Earth Approaches to Vertebrate Paleontology

Abstract

Vertebrate fossils are commonly found in buried soils (paleosols) of the ancient landscapes they inhabited. Study of these soils (paleopedology) can provide information important to the interpretation of vertebrate fossils, as illustrated here with a review of biostratigraphic, taphonomic, paleoecological and evolutionary studies of Oligocene fossil soils and vertebrates in Badlands National Park, South Dakota. A significant advantage is gained from the fact that paleosols are, by definition, in place. Fossils within them are less likely to have been resorted from rocks of different age than fossils in deposits of lakes and streams. Soil formation punctuates the sedimentary accumulation offloodplain deposits, and thus provides a limit to effective biostratigraphic resolution of sequences of paleosols containing fossil vertebrates. Paleosols also are preservational environments for fossils. Bone is best preserved in calcareous paleosols of dry climates. Assemblages from less calcareous paleosols are subject to severe bias against preservation of small bones. Because of their higher surface-to-volume ratio, these are more prone to dissolution than large bones. Paleosols also provide records of ancient habitats of vertebrates, particularly their local vegetation and geomorphic setting. Such information is useful not only for paleoecological reconstructions, but as evidence of selection pressures effective in mammalian evolution. Temporal resolution of sequences of paleosols also can be a critical limitation on studies of the rate of evolution of mammalian fossils.