Family-level ecometrics reveal functional trait stability in Miocene artiodactyls despite environmental change in the Mojave region

Functional traits are indicators of how species interact with their environment, and changes in community-wide trait composition are often associated with environmental change. This relationship provides a means to track ecological dynamics even in cases when taxonomic resolution is limited. The artiodactyl astragalus is a weight-bearing skeletal element that is key to hindlimb movement, and also preserves morphological signals of body size and cursoriality based on the understanding that relatively short astragali in modern artiodactyls are correlated with open habitats. We examined astragalar morphology in fossil artiodactyls (Antilocapridae and Camelidae) from the Miocene Dove Spring Formation (12.5 to 8.5 Ma) to assess whether locomotor traits responded to a known regional shift from a forest-dominated landscape to a patchwork of woodland and grassland habitats. We found that despite ongoing aridification and local changes in vegetation during the middle to late Miocene, the community-wide astragalar functional ratio remained stable, suggesting that environmental changes were insufficient to drive directional morphological adaptation. Clade-specific analyses showed that camelids possessed consistently higher functional ratios than antilocaprids, reflecting divergent locomotor strategies that likely corresponded to differences in body size, habitat use, or mobility. These results suggest that behavioral plasticity—including range tracking and habitat selection—may buffer large herbivores against extinction or adaptation under regional environmental stress in fragmented, heterogeneous landscapes. This study demonstrates the potential of ecometric analyses to reveal ecological patterns in fossil assemblages with limited taxonomic resolution and emphasizes the utility of linking functional morphology with paleoenvironmental data to reconstruct mammalian response to long-term environmental change.