Researchers have used mathematical models to analyze and classify shel
ls and, by simulating hypothetical forms, to test specific theories ab
out them. Based on an analogy in which these mathematical models are c
onsidered as species, I construct a data set and derive a cladogram of
shell models. This analysis provides a concise, graphic review of the
major works in the discipline of shell modeling. Interpreting the res
ults phylogenetically, I demonstrate that an evolutionary model provid
es insights into the different approaches taken by researchers, permit
s the differentiation and classification of models into clades of form
and growthlike ''species,'' and allows the identification of anagenes
is and historical constraints in the development of ideas in the disci
pline of shell modeling.