You better run: macroevolutionary study reveals the differentiated impacts/constraints of mechanics, physics, and history in ruminants’ ankle bone

Abstract

Abstract The astragalus is a hinged bony organ common to many tetrapods. Its morphology is constrained by several factors: allometry, environment, and phylogeny. Morphological features connected to these factors are discussed here for one of the most successful large mammal groups today, for ruminants. 3D Geometric morphometrics not only confirms previous linear measurements but also identifies other areas that were previously undetected by biometrics data. The relative height of the distal trochlea is influenced by the body mass. The functional length of the astragalus and certain articular and ligament insertion surfaces are influenced by the preferred mode of locomotion and thus represent habitat. Clade-specific characters were identified in this study. Cervidae have a more “bean-shaped” distal facet (articulation surface to calcaneus) while Bovidae have an “egg-shaped” one. These zones do not seem to have been affected by the previous constraints. Neutral and random evolution can take place on these structures and provide essential information for phylogeny. These new data can complement the character matrices used in cladistics.