FLUVIAL FLOATATION OF TERRESTRIALLY DERIVED BODIES, BONES, AND PARTS AND ITS PALEONTOLOGICAL IMPLICATIONS

Post mortem transport alters the temporal and spatial resolution of fossil and archaeological skeletal assemblages, and as such, it is important to identify if any transport has occurred prior to assemblage analysis. Transport of bodies (bloat and float), multiple connected bones, or individual bones, has typically been inferred based on preferred orientations, taphonomic modifications (abrasion), and the remains of organisms deposited in environments outside the organism’s life habitat. The process of floatation occurs rapidly, can potentially transport remains hundreds of miles in a short time (days to weeks), and does not leave traces of its action on remains. As such, it is presently impossible to identify remains that have experienced floatation during part of their taphonomic history. However, if floatation is rare or uncommon, this taphonomic process could potentially be ignored.

During surveys of 13 rivers, 10 bodies of terrestrial organisms were found, eight of which were floating. Similarly, 33 articulated units were observed, only one of which was floating. No isolated bones were observed floating, however of the 474 isolated bones observed, three were deposited in locations consistent with floating (in or on vegetation). During specimen cleaning for research and comparative anatomy collections, bones have been observed floating for durations from minutes to months. These observations combined with many forensic case reports demonstrates that bones, body parts, and full bodies frequently float, and float for long durations of time, often for long distances. Many investigators have observed bone floatation reporting durations from seconds to months, and remains slowly hydrating over time. In addition, bones can develop floatation during decay as decay gases build up within them and reduce their density.

Since bodies, parts, and isolated bones can float, and can float multiple times during decay, floatation should seriously be considered during taphonomic history reconstruction before and during assemblage analysis. Articulation does not indicate remains are in situ for complete or mostly complete organisms, and disarticulated skeletal material could easily have floated multiple times after death.