Histology of the right tibia and fibula of Mei long, DNHM D2514.

A, cross-section of tibia and fibula in articulation. B, partial cross-section of fibula. C, partial cross-section of tibia. Note two zones of fibro-lamellar bone separated by a LAG in the tibia and the largely avascular lamellar bone that marks the periphery of both elements. The latter can be interpreted as an external fundamental system. Abbrevaitions: el, endosteal lamellar bone; fl, fibro-lamellar bone; fl1, first and interior zone of fibro-lamellar bone; fl2, second and more exterior zone of fibro-lamellar bone; LAG, line of arrested growth; mc, medullary cavity; pl, peripheral lamellar bone. Scale bars equal 0.5 mm in A and 0.2 mm in B and C.