Fractal-like geometry as an evolutionary response to predation?

Abstract

Fractal-like, intricate morphologies are known to exhibit beneficial mechanical behavior in various engineering and technological domains. The evolution of fractal-like, internal walls of ammonoid cephalopod shells represent one of the most clear evolutionary trends toward complexity in biology, but the driver behind their iterative evolution has remained unanswered since the first hypotheses introduced in the early 1800s. We show a clear correlation between the fractal-like morphology and structural stability. Using linear and nonlinear computational mechanical simulations, we demonstrate that the increase in the complexity of septal geometry leads to a substantial increase in the mechanical stability of the entire shell. We hypothesize that the observed tendency is a driving force toward the evolution of the higher complexity of ammonoid septa, providing the animals with superior structural support and protection against predation. Resolving the adaptational value of this unique trait is vital to fully comprehend the intricate evolutionary trends between morphology, ecological shifts, and mass extinctions through Earth’s history.

Investigations into 3D-printed nautiloid-inspired pressure housings

“…For example, FEA has indicated that increased septal complexity results in increased principal stress on the septa but increased the tolerance to point loads, which mimic biting forces from known predators [15,19]. Thus, predation rather than tolerance to hydrostatic pressure may have shaped the evolution of increased septal complexity [20], which complicates interpretations of the relationship between shell form and bathymetry in either relative or absolute terms. Using similar FEA methodologies and in contradiction to previous findings, more septal folds have also been found to decrease the principal stress on individual septa [16].…”