Calcar

A picture illustrating the location of the calcar on a bat.

The calcar, also known as the calcaneum,^[1] 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,^[1][2] this is to help spread the interfemoral membrane,^[3] which is part of the wing membrane between the tail and the hind legs.

This membrane can form a basket or pouch to help catch and hold insects captured in flight.^[3] The oldest known ancestor to present day bats, Icaronycteris index, apparently did not have a calcar or spur as evidenced by fossil remains.^[4]

Calcar (Femorale) also refers to the dense, vertically orientated bone present in the posteroemedial region of the femoral shaft superior to the lesser trochanter of the femur.

References

1. ↑ 1.0 1.1 The Anatomy of Bats
2. ↑ The Handbook of British Mammals (ASIN B000WPL1CO)
3. ↑ 3.0 3.1 Encyclopedia Smithsonian: Bat Facts
4. ↑ Ontogeny, Functional Ecology, and Evolution of Bats (ISBN 978-0-52-162632-3)