Fig. 4.

Maximum-likelihood estimates of ancestral shell patterns. Shells of living species are displayed at the tips; to the right of these are shells “grown” in the computer by using the neural-network model and the fitted parameters. By using a Brownian motion model for the evolution of continuous traits, the maximum-likelihood value was estimated for each neural network parameter at each node. The neural network model was used to produce the shells using the estimated parameters for each node. Color is not part of the neural network model, so it was added independently to the models of living shells, and then mapped onto the phylogeny (using maximum likelihood) as a binary trait (black/white or brown/white). The text includes further details.