Pterosaur Carpal bones
Pterosaur carpal bones are usually 3 in number.
The Proximal Carpal (PC) articulates with the Radius and Ulna bones of the wing. This is the carpal nearest to the animals body.
The Distal Carpal (DC) articulates with the Wing Metacarpal. There is a peg like process on the end of the wing metacarpal which fits into a recess in the Distal Carpal.
The Lateral Carpal (LC) is a small bone located at the edge of the distal carpal. It is the articular location for the Pteroid bone. This can be seen in the general diagram below.
The carpal bones form a structure which allows a limited few degrees of movement at the wrist joint. They are essentially two apposing saddle shaped bones which rock in two planes. This can be illustrated in the sketch below.
Peter Wellnhofer was one of the leading pioneers of bone structure in Rhamphorhynchus. He mapped out the bone forms and joints in a clear and precise way to give a better understanding of the way the pterosaur skeleton fitted together.
The illustration on the left appeared in "Handbuch der Paläohepetology, Teil 19" and it shows the general structure of the wrist joint and carpals of Rhamphorhynchus.
The proximal carpal is seen articulating with the Ulna and Radius. This carpal in turn articulates with the Distal Carpal in a saddle like gliding joint.
The Lateral Carpal can be seen in the diagram to the left of the Distal Carpal. The two part pteroid bone is articulating with this small carpal, and the metacarpals of the clawed hand are all in close proximity to this small lateral carpal.
The individual distal and proximal carpals are difficult to visualise in the joint associated diagram, so a disarticulated illustration is given below. Here, the scale bar is 1cm long and the carpals shown are those of Rhamphorhynchus. The articular facets (f) are marked for the Radius (fr), Ulna (fu) and Wing Metacarpal (f mcIV).