Wombat Bone

A 100-micron thick section from the femur (thighbone) of Vombatus ursinus, a wombat. Wombats are members of Marsupiala, the highly diverse group of mammals that includes pouched animals such as the kangaroo, koalas, opossums, and many other species. Native to Australia, wombats are powerful, robustly built, dog-sized diggers. The thickness of the bone seen here is a good indication of the strength of a wombat. The colors in this image represent differences in the orientation of collagen fibers present in the bone, as viewed in circularly polarized light. Despite their close evolutionary relationships to one another, marsupials are expected to show a diversity of collagen fiber patterns, depending on the way that they move during life and the resulting forces to which their bones are subjected.