FIGURE 5. Heterochronic modelling experiment 2 in Heterochrony in helicoid spiral cones: a computer model for demonstrating heterochronic evolution

FIGURE 5. Heterochronic modelling experiment 2. The "ancestor" on the left has parameters W0=1.1, ΔW=0.05, D=0, S=2.3, T'0=2, ΔT'=-0.03, and has 10 whorls. It has a form, including the slightly concave profile of the spire, which is similar to some members of the Family Volutidae. The next simulations are "descendants" derived from this by successive increments of acceleration (relative scales x 0.5, x 0.225, x 0.0875, respectively). All of these have parallels in the Volutidae, with the final form resembling the giant volutids in the genus Melo. The observation that the simulation predicts the large size of the final form supports the heterochronic hypothesis in the evolution of these gastropods.