Calcar
![A picture illustrating the location of the calcar on a bat.](/Images/godic/202501/02/Bat_calcar5245.jpg")
The calcar, also known as the calcaneum, is the name given to a spur of cartilage arising from inner side of ankle and running along part of outer interfemoral membrane in bats, This is to help spread the interfemoral membrane, which is part of the wing membrane between the tail and the hind legs.