SHELL ALIGNMENT FOR THE MORPHOMETRIC ANALYSIS OF HIGH-SPIRED GASTROPODS

A significant problem often impedes the morphometric analysis of high- spired gastropods. It is usually not Possible to obtain large samples of complete specimens. Without the ontogenetic landmarks provided by e arly whorls it is difficult to align incomplete specimens to compare h omologous whorls. We discuss several methods that allow alignment of m orphometric data taken from incomplete specimens of high-spired gastro pods. We evaluated these methods by treating a set of complete specime ns as incomplete. Two methods produce reliable alignments. One of thes e uses an ontogenetic function of the whorl expansion rate to estimate missing whorls; the other aligns whorls of similar heights. Both prod uce reasonably precise and accurate alignments, but under different as sumptions. Once a set of specimens has been aligned, it can be subject ed to conventional statistical analysis using accepted conventions to deal with missing data.