I was interested in the comments about Sr/Ca ratios in fossils and stable isotope work in general. Andrew Millard suggested that there are difficulties in interpreting the signals. I may not be up to date on this but I remember that sequential washes were used to remove the diagenic signal and the remaining signal was taken to be an indication of the biogenic ratios. This seemed to make sense because there were differences between definte herbivores and definite carnivores from the same deposits (presumably subjected to the same diagenic regime). This leaves the possibility that bones are entering the deposit with different signals based less on their trophic level but more on differences between the background levels of trace elements/ rare isotopes between the localities where they 'grew' their bone/ laid down the mineral signal; i.e. a suprious signal ante-mortem, or there are some other post-mortem processes such as different bone chemistry unrelated to diet leading to a 'false' signal in the fossils even after all the washes. Both these 'spolier' hypotheses seems unlikely and in any case, the first one would show up with more sampling... are their grounds for the second? I would love to know more as it is an intriguing line of evidence. Can Dr Millard, (or anyone else) fill us in or cite some of the up to date references so we (I) can read some of the criticism of this provoking work. Mark -- Mark Leney New College University of Oxford