How heating and cooling and wetting and drying can destroy dense faunal elements and lead to differential preservation

Recent taphonomic research has demonstrated that bulk bone density significantly determines survivability in many archaeological and paleontological contexts. Researchers often assume that higher density skeletal elements invariably preserve better than lower density skeletal elements. This assumption, however, is not universally valid. Here we present data on the taphonomy and preservation of assemblages from the Geelbek Dunes of the Western Cape Province, South Africa. These data indicate that skeletal preservation of fossil assemblages from deflation hollows can reflect an unexpectedly high proportion of porous, low density skeletal parts. High density skeletal parts including teeth and the shafts of long bones often shatter as a result of the repeated thermal shock and wetting and drying of the kind observed at Geelbek. This effect is greatest for highly mineralized bones from large mammals. The data from Geelbek demonstrate that survivability is affected by the size of the animal. Small mammals are represented by high proportions of non-mineralized, dense, skeletal parts, especially long bones.