3D PRINTING REVEALS STRENGTHS AND WEAKNESSES OF PREY SHAPE DURING THE MESOZOIC MARINE REVOLUTION

The shapes of snail shells have long been hypothesized to have evolved, in part, due to predation pressures from shell-crushing molluscivores. During the Mesozoic (250-65 Ma) specifically, the apparent diversification of durophagous fishes is thought to have created “arms races” which drove decreases in the commonality of “weak” shell shapes and increases in the commonality of “strong” shapes. Across various taxa with different material properties, open-coiling, umbilicate, and planisprial forms disappeared while other forms, like turbinate shells, persisted. Although these shifts towards “sturdier” shell forms in are used as a global example of escalation during the Mesozoic Marine Revolution, the relative strength of these geometries has never been explicitly tested. While previous experiments were confounded by differences in life history, material properties, and other variables, we used 3D printing to create physical models of mathematically-idealized shell shapes and experimentally test their strength in isolation. Our gypsum powder prints were created using modified equations derived from “Raup Space” and scaled to control factors like size and thickness. These models were crushed using an Instron to test their strength under compression by a simulated vertebrate predator. We find that although planisprial shells were exceptionally weak, other shapes were stronger than previously predicted without experimental testing. Our results suggest that vertebrate predators alone are unlikely to have driven the decrease in abundance of these groups over the Mesozoic.