We continued direct morphological studies of the canid coxofemoral joint, considering early-life spatial relationships around the locus of the proximocaudal joint capsule insertion. Our primary goal was to elucidate the post-natal developmental gross anatomy of the proximocaudal femur, in juveniles across Canidae. From an original database of 267 independent (museum) specimens from 11 canid taxa and one hybrid taxon, we identified 29 ancient or modern candidate juvenile specimens (9 taxa and one hybrid taxon). Based on optimal ability to recognize landmarks, the best photographic data were categorized into 5 groups of 4 each (n = 20). The data groups approximated early juvenile, early-mid juvenile, mid-juvenile, mid-late juvenile; and young adult stages.

In this descriptive photographic essay, we demonstrate the developmental spatial proximity among (a) the dorsal meeting of the respective lateral and medial extensions from the growth centers of the femoral head and greater trochanter; (b) the caudodorsal aspect of the coxofemoral joint capsule attachment; (c) a segment of the proximocaudal femoral shaft physis; and (d) an eventual associated mineralized prominence. The latter occurs frequently but not universally, suggesting natural population variability across taxa.

Across taxa and juvenile age categories, the morphology thus supports developmental conservation among ancient and modern Canidae. The biomechanical and biological cause-effect implications are not yet clear. For zoological purposes, we apply the term post-developmental mineralized prominence (PMP) to the residual caudolateral surface feature. We extend the original anatomical work of Morgan in zoological and phylogenic arenas, using direct observation of cleared skeletal specimens.