From armadillos to sloths: Patterns and variations in xenarthran coronary anatomy

Species of the superorder Xenarthra play a vital ecological role in the Neotropics. Despite their evolutionary significance, anatomical studies on their coronary circulation remain scarce. This study investigated the coronary anatomy of 82 hearts from nine Xenarthra species across the Dasypodidae, Myrmecophagidae, and Bradypodidae. The right coronary artery (RCA) originated from the right aortic sinus in all specimens and typically emitted atrial, ventricular, and marginal branches, as well as the subsinuosal interventricular branch (94.9%). A common trunk of the left coronary artery (LCA) was identified in 89% of hearts, typically divided into paraconal interventricular and circumflex branches; when absent, these branches arose directly from the aortic sinus. Vessels coursed predominantly epicardially (74.4%), with intramyocardial paths and myocardial bridges restricted to PIVB. Anastomoses between interventricular branches were present in 28.6% of cases. Coronary dominance was predominantly balanced (92.3%), although classifications varied across the three criteria applied, underscoring method dependence. Quantitative comparisons revealed significant interspecific variation in the number and distribution of ventricular branches, with Cabassous tatouay exhibiting the highest mean from the PIVB. Family-level patterns and ecological associations were observed, including anastomoses restricted to Myrmecophagidae, simplified branching in sloths consistent with low metabolic rates, and greater redundancy with intramyocardial courses in fossorial or foraging taxa. This study advances the understanding of xenarthran coronary anatomy and provides a comparative framework for evolutionary interpretation and veterinary care of these often-threatened mammals.