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The fossil record represents the world’s largest historical dataset of biodiversity. However, the biomechanical and ecological potential of this dataset has been restricted by various unique barriers obstructing experimental study. Fossils are often partial, modified by taphonomy, or lacking modern analogs. In the past, these barriers confined many studies to descriptive and observational techniques. Fortunately, advances in computer modeling, virtual simulations, model fabrication, and physical experimentation now allow ancient organisms and their biomechanics to be studied like never before using “Defossilized Organismal Proxies” (DOPs). Although DOPs are forging new approaches integrating ecology, evolutionary biology, and bioinspired engineering, their application has yet to be identified as a unique, independent methodological approach. We believe that techniques involving DOPs will continue revolutionizing paleontology and how other related fields interact with and draw insights from life’s evolutionary history. As the field of paleontology moves forward, identifying the framework for this novel methodological development is essential to establishing best practices that maximize the scientific impact of DOP-based experiments. In this perspective, we reflect on current literature innovating the field using DOPs and establish a workflow explaining the processes of model formulation, construction, and validation. Furthermore, we present the application of DOP-based techniques for non-specialists and specialists alike. Accelerating technological advances and experimental approaches present a host of new opportunities to study extinct organisms. This expanding frontier of paleontological research will provide a more holistic view of ecology, evolution, and natural selection by breathing new life into the fossil record. 

Abstract The internal architecture of chambered ammonoid conchs profoundly increased in complexity through geologic time, but the adaptive value of these structures is disputed. Specifically, these cephalopods developed fractal-like folds along the edges of their internal divider walls (septa). Traditionally, functional explanations for septal complexity have largely focused on biomechanical stress resistance. However, the impact of these structures on buoyancy manipulation deserves fresh scrutiny. We propose increased septal complexity conveyed comparable shifts in fluid retention capacity within each chamber. We test this interpretation by measuring the liquid retained by septa, and within entire chambers, in several 3D-printed cephalopod shell archetypes, treated with (and without) biomimetic hydrophilic coatings. Results show that surface tension regulates water retention capacity in the chambers, which positively scales with septal complexity and membrane capillarity, and negatively scales with size. A greater capacity for liquid retention in ammonoids may have improved buoyancy regulation, or compensated for mass changes during life. Increased liquid retention in our experiments demonstrate an increase in areas of greater surface tension potential, supporting improved chamber refilling. These findings support interpretations that ammonoids with complex sutures may have had more active buoyancy regulation compared to other groups of ectocochleate cephalopods. Overall, the relationship between septal complexity and liquid retention capacity through surface tension presents a robust yet simple functional explanation for the mechanisms driving this global biotic pattern.