pdf: http://www.research.plymouth.ac.uk/paleopa....09b.pdf

The O isotope compositions of well-preserved Jurassic fish otoliths from Wootton Bassett, UK, provide upper-ocean paleotemperatures that are comparable with those derived from the isotopic analysis of lish tooth phosphates, providing independent scrutiny of such paleotemperatures. O-isotope otolith temperatures in excess of 30 "C also rival temperatures associated with the middle Cretaceous thermal maximum. The negative carbon isotopes of the otoliths may point to a freshwater influence and potentially migratory nature of the fish. However, given the large departures from equilibrium fractionation toward more negative carbon values reported from modern marine fish, authors consider temperature interpretations to be robust and representative of the marine depositional environment. Depleted C isotope values, perhas, suggest that the otoliths examined in this study belong to fish with high metabolic rates.