A pseudoarthrosis in the forelimb of a sloth (Choloepus didactylus). American Museum novitates ; no. 2439

Abstract

"A pseudoarthrosis between the left radius and humerus resulting from a dislocation of the elbow is described in Choloepus didactylus. The shape of the radial articular surface had changed from a concave to a convex surface and a new cup-shaped articular surface had formed on the shaft of the humerus. The pseudoarthrosis was apparently fully functional at the time the animal was collected. The development of the pseudoarticulations through the process of physiological adaptation following dislocations of bones in which a nonarticular bony surface is modified into an articulating surface provides an insight into the evolutionary mechanisms involved in the origin of many new articulations, such as the dentary-squamosal joint in mammals"--P. 9-10.