Reading the canid skeletal story: Coxofemoral joint pathology, and suggested implications for the phylogenetic and natural history of taxa

ABSTRACT We evaluated subtle-to-incipient pathology traits in coxofemoral joints from dry bone museum specimens of: Vulpes lagopus; Vulpes; Nyctereutes procyonoides; Urocyon cinereoargenteus; Canis lupus familiaris; and Canis latrans. Multiple intra-articular structures were evaluated on acetabula and proximal femora. Primary observations included multifocal, variable osteophyte-like formations; osteophyte-like rimming of articular margins and femoral head (ligamentum teres attachment); and rough or worn bone. Within limitations on valid statistical applications, we observed little difference among the high trait frequencies across taxa, aligning with previous morphological observations. Additionally, for this study, we evaluated the known history of the taxa, from deep time to the present, to consider our data in a phylogenetic context. Potential introgression over the evolution of Canidae, along with early history of the canid genome, likely supported broad and deep conservation of pathophysiological processes associated with observable pathology at the same intra-articular foci, across taxa. We also evaluated the modern natural histories of the taxa, noting that coxofemoral joint impacts of their respective life habits did not appear to influence pathology trait outcomes differentially. We conclude that conservation of the physiology underlying subtle and incipient coxofemoral joint pathology that did not segregate among taxa. We hypothesize that the intersecting basic biology of growth-development and insult response, over long geological time, may owe in part to the evidently long histories of hybridization and generally high historical gene flow, with high levels of heterogeneity. These data argue for new research to advance an interdisciplinary, integrated understanding of relationships among canid growth-development, incipient-to-subtle joint pathology, influences of natural histories across related taxa, and implications for genomic interrelationships. ### Competing Interest Statement The authors have declared no competing interest.