ANATOMY OF THE PROPATAGIUM - THE GREAT HORNED OWL (BUBO-VIRGINIANUS)

Skinfolds and feathers form the profile of the avian airfoil. The wing of birds has a nearly flat profile from shoulder to carpus, without t he presence of the propatagium. The propatagium is the largest skinfol d of the wing; it fills the angle formed by the partially flexed elbow , and with its feathers forms a rounded leading edge and dorsally camb ered profile added to the cranial aspect of the wing. The propatagium is variably deployed, relative to elbow extension, in flight; support for its cambered shape is maintained by multilayered collagenous and e lastic tissue networks suspended between leading edge and dorsal anteb rachium. The leading edge ligament (Lig. propatagiale) courses from de ltopectoral crest to carpus and, with its highly distensible center se ction, supports the leading edge of the propatagium across a range of wing extensions. The elbow extension limiting ligament (Lig. limitans cubiti) courses from deltopectoral crest to proximal antebrachium and limits maximum elbow-extension. M. deltoideus, pars propatagialis inse rts on the proximal end of the common origin of the propatagial ligame nts and, by way of the insertions of the two ligaments, coordinates (1 ) automatic flexion/extension actions of the elbow and wrist, (2) prop atagial deployment, and (3) tension along the length of Lig. propatagi ale supporting the leading edge. (C) 1994 Wiley-Liss, Inc.