A NEW SYSTEM FOR THE CLASSIFICATION OF PRESERVATIONAL QUALITY OF FOSSIL ASSEMBLAGES

A new system for classifying the preservational quality of fossil assemblages has been developed which is based on the damage types responsible for a reduction in taxonomic identifiability. Included in this new system are a set of guidelines, based on computer simulations and field observations, for comparing paleoecological data from assemblages having different states of preservation.

It is long-suspected that quality of preservation (e.g. original shell material versus molds; pristine versus degraded shape and ornamentation; whole shells vs. fragments) plays a significant role in biasing paleoecological data (e.g. species richness; abundance structure; evenness). Despite this, many paleoecological studies continue to neglect preservational quality as a basic element of assemblage description. One reason for this may be that no system to classify preservational quality currently exists that can readily be applied in the field--existing systems typically require careful examination of each specimen to collect multiple different types of taphonomic data, which is too time-consuming for most non-taphonomists. Additionally, it is not clear that the data collected in these systems for assigning a “grade” are actually those that are most relevant to assessing bias in biological information. Here, I present a new system for classifying the preservational quality of bivalve and brachiopod dominated assemblages. Importantly, this system is sufficiently simple to use during basic field work, and is based on factors identified as having the most significant effects on the taxonomic identifiability of fossil specimens, and thus on the quality of paleoecological data.