Introduction

Ecological morphology (ecomorphology) is a powerful tool for exploring diversity, ecology, and evolution in concert (Wainwright, 1994, and references therein). Alpha taxonomy and diversity measures based on taxon counting are the most commonly used tools for understanding long-term evolutionary patterns and provide the foundation for all other biological studies above the organismal level. However, this provides insight into only a single dimension of a multidimensional system. As a complement, ecomorphology allows us to describe the diversification and evolution of organisms in terms of their morphology and ecological role. This is accomplished by using quantitative and semi-quantitative characterisation of features of organisms that are important, for example, in niche partitioning or resource utilisation. In this context, diversity is commonly referred to as disparity (Foote, 1993). The process of speciation, for example, can be better understood and hypotheses more rigorously tested if it can be quantitatively demonstrated whether a new species looks very similar to the original taxon or whether its morphology has changed in a specific direction. For example, if a new species of herbivore evolves with increased grinding area in the cheek dentition, it can either occupy the same area of morphospace as previously existing species, suggesting increased resource competition, or it can occupy an area of morphospace that had previously been empty, suggesting evolution into a new niche. This example illustrates a situation where speciation did not just increase the number of taxa, but also morphologic and ecologic diversity. In turn, this quantitative information can be used to test speciation hypotheses in the extant fauna as well as the fossil record suggested by previous studies using molecular data and habitat reconstruction (Gaubert and Begg, 2007).