ON THE TOPIC OF ECOLOGIC SPECIALIZATION
Previous work quantified specialization in fossil clades using the range of facies occurrences as a proxy for niche breadth. A sliding scale termed the Eurytopy Index (EI) represents the number of recorded facies for each species. The EI of a clade is the mean number of facies occupied by the species within a clade. Species with a wide range of facies occurrences were assumed to have had wide niche breadth and, thus, were more or less generalist species. EI is a way to quantify a certain kind of specialization but it remains to be seen if paleontological specialists equal in any meaningful way to neontological specialists.
To test the degree to which these concepts overlap, EI was calculated for extant neogastropod clades. Subsequently, an extensive literature review provided information on the diets of the same clades. Preliminary results suggest facies dependence may be an abiotic proxy for tropic specialization but because other influences (refugia from predators, physiological restraints, basinal containment of endemics, latitudinal clines of competition) cannot be ruled out. Implications for paleontologists and neonatologists are discussed.