Classifying echinoid skeleton models: testing ideas about growth and form

Theoretical morphology is the scientific field in which researchers model organism growth and form. The field is developed well in studies on skeletons, especially shells. Researchers have contributed echinoid skeleton models to the field, but these have yet to be recognized collectively. We present herein the first comprehensive review for echinoid skeleton models in theoretical morphology. We apply a phylogenetic systematic analysis to those models, use the resulting consensus cladogram to classify and interrelate the models in an analogy in which they are likened to fossil specimens in a biostratigraphic record, and utilize the biostratigraphic metaphor to define trends within theoretical morphology as it applies to echinoid skeleton models.