Comparison of the bone histology of the prosauropod Plateosaurus from the Triassic of Frick (Switzerland) and the largesauropod from the Triassic of Thailand.(a) Cross section of a Plateosaurus humerus at mid-shaft, showing a large medullary cavityand clear growth cycles which are more closely spaced with increasing age of the individual; rectangle marks location of samplein (b).(b) Detail of cortical bone; the cortex consists of laminar fibro-lamellar bone with regularly spaced LAGs.(c) Cortex of thelarge sauropod humerus, note the lack of obvious growth marks; rectangle marks location of sample in (d).(d) Detail; the corticalbone is of the laminar fibro-lamellar type seen in later sauropods.