Identification of a Trade-Off Structured Functional Spectrum in Ordovician Conodonts: Beyond Passive Filling and Competition Models

The Great Ordovician Biodiversification Event (GOBE) has traditionally been interpreted in two diferente ways as a passive filling of available ecospace or as a process structured by ecological competition and niche partitioning. However, resolving this debate also requires, among other factors, an understanding of how functional diversity is organised within expanding marine communities. In this context, transverse sections of 60 euconodont P1 coniform elements from across the Ordovician are analysed using elliptic Fourier analysis and beam theory. This combined approach allows us to quantify early morphological diversification and biomechanical performance of coniform conodonts within an ecological and evolutionary framework.Specifically, our results reveal a continuous functional spectrum structured by trade-offs in mechanical performance, rather than discrete functional categories. Resistance to anteroposterior bending, dorsoventral bending, and torsion is distributed along smooth gradients in morphospace, indicating that morphological variation translates into continuous variation in biomechanical efficiency. Importantly, only a limited number of taxa approach optimal mechanical performance, while most occupy suboptimal regions of the functional space. This pattern suggests that functional diversification in Ordovician conodonts was constrained by trade-offs among competing mechanical forces, preventing convergence towards a single optimal design. Therefore, the ecological structure during the GOBE, at least in conodont assemblages, cannot be fully explained by either passive filling of ecospace or strict competitive partitioning. Instead, it is better described by a gradient-based organisation of functional traits governed by biomechanical constraints. This provides a novel perspective on the nature of ecological diversification during one of the most important radiation events in Earth history.