Fig. 6. Summary of the capacity for the oxidation of trimethylamine to trimethylamine oxide (TMAO), indicative of TMAO synthetic capacity, in chondrichthyian fishes (elasmobranchs and chimaeras) arranged phylogenetically. The tree is simplified from Winchell et al. (Winchell et al., 2004) and, for simplicity, orders where no data on the oxidation of trimethylamine are available have not been included. *TMAO synthesis was assessed in vitro; TMAO synthesis was assessed by in vivo conversion of labeled precursor; –, below limits of detection or questionable synthetic capacity; +, significant TMAO synthesis present. Values in parentheses indicate the source of data: ¹Baker et al., 1963; ²Goldstein et al., 1967; ³Goldstein and Funkenhouser, 1972; ⁴Goldstein and Dewitt-Harley, 1973; ⁵Treberg and Driedzic, 2002; ⁶present study.