The significance of vertebrate microfossil size and shape distributions for faunal abundance reconstructions: a Late Cretaceous example

Abstract

Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cretaceous Judith River Formation of south-central Montana illustrate that even when located in similar sedimentary facies, concentrations of vertebrate microfossils may exhibit strikingly different taphonomic profiles. Degrees of microfossil size and shape sorting may vary even among sites from the same sedimentary facies. In some instances, such variations may make it impossible to disregard taphonomic causes for differences sites exhibit in paleofaunal abundances. To limit the possibility that taphonomically generated faunal differences might be mistaken for true differences in paleoecology, comparisons of paleofaunal abundances should be restricted to microvertebrate sites both from similar sedimentary facies and with similar profiles of fossil sizes and shapes.