A review of preservational variation of fossil inclusions in amber of different chemical groups

Fossils in amber are a particularly important and unique palaeobiological resource. Amber is best known for preserving exceptionally life-like fossils, including microscopic anatomical details, but this fidelity of preservation is an end-member of a wide spectrum of preservation quality. Many amber sites only preserve cuticle or hollow moulds, and most amber sites have no fossils at all. The taphonomic processes that control this range in preservation are essentially unknown. Here, we review the relationship between amber groups and fossil preservation, based on published data, to determine whether there is a correlation between resin type and aspects of preservation quality. We found that ambers of different chemistry demonstrated statistically significant differences in the preservational quality and the propensity of a site to contain fossils. This indicates that resin chemistry does influence preservational variation; however, there is also evidence that resin chemistry alone cannot explain all the variation. To effectively assess the impact of this (and other) variables on fossilisation in amber, and therefore biases in the amber fossil record, a more comprehensive sampling of bioinclusions in amber, coupled with rigorous taphonomic experimentation, is required.