Assessing relative abundances in fossil assemblages

The relative abundances of taxa or skeletal elements in a fossil assemblage can provide important information concerning the palaeoecology and taphonomy of the assemblage. However, these relative abundances must be estimated from samples of the assemblage, rather than measured directly. The sampling error this produces decreases the accuracy with which relative abundances can be estimated from the fossil record. Using the multinomial distribution it is possible to place constraints on the accuracy of estimation of relative abundance, provided that two out of three key parameters (sample size, required degree of similarity and confidence level) are known. Applying this methodology to the fossil record it can be shown that in order to be 95% confident the taxon relative abundances of a fossil assemblage lie within 5% of those found in a sample, 534 individuals must be collected. This methodology enables the assessment of published relative abundance estimates and the development of sampling protocols for future studies.