David M. Raup's three-parameter model revolutionized our understanding of shell morphology by reducing the infinite variety of mollusk shells to just three geometric parameters: whorl expansion rate (W), distance from coiling axis (D), and translation rate (T).

This morphospace visualization allows exploration of theoretical shell forms, many of which don't exist in nature. By adjusting the three parameters, you can navigate through possible shell geometries and understand the constraints that shape biological form.

Key concepts include: theoretical morphology, parametric modeling, evolutionary constraints, shell geometry, and the relationship between mathematical possibility and biological reality.