In looking up descriptions of bats, I encountetered the term "calcar" which might be "keeled" or not.
It took me quite a while to find a description of this term.
"
The hind legs of many bats are partially or completely joined by a membrane, the uropatagium, which also may enclose the bony
tail. It is supported by the legs, the tail skeleton, and by the calcar, a special cartilaginous extension of the wrist. The calcar
sometimes bears a distinctive projection called a keel. In some species, both the uropatagium and calcar are absent.(the uropatagium is a portion of flight membrane between hind legs and midline.)
But if you look at picture in this URL, to your left there is a label "metacarpal" which must = "wrist".
http://animaldiversity.ummz.umich.edu/media/anat/bat_wings.jpg