On a visit to a local crypt (Gloucester, England), the cryptkeeper discussed the overfill of burials on their holy grounds. The bodies were exhumed, the skull was collected and moved inside the crypts along with the femur and the rest of the bones were disposed of.
The significance of the skull is obvious, but why the femur? This practise appears to take place across countries, religions even continents. Is it just a measure of approx height of the deceased?
Long bones such as the femur do factor in body size measurement formulae. Also, growth and fusion of the epiphysis on long bones (it is very distinct on the femur, especially) is an indicator of the age of the deceased. So the combination of information from the skull (including teeth) and the femur are instrumental in learning more about the physiology, etc. of the subject.
Source: a class on Human Osteology; I can find more concrete, text sources if need be.