The degradation and preservation affecting the biomarker record of ancient metazoa are not fully 33understood. We report on a five month experiment on the fate of fatty acids (FAs) during the degradation 34of recent whale vertebrae (Phocoena phocoena). Whale bones were analysed for extractable FAs and 35macromolecularly bound n-acyl compounds. Fresh bone showed extractable FAs dominated by 3616:1x7c, 16:0, 18:1x9c and 18:0. Calculated degradation rate constant (k) values showed a rapid 37decrease in FA concentration, with k values higher for unsaturated than for saturated compounds 38(e.g. 0.08/day for 18:1x9c, 0.05/day for 16:0). The appearance or increased abundance of distinctive 39methyl branched (e.g. i/ai-15:0 and -17:0, 10Me-16:0) and hydroxy FAs (e.g. 10OH-16:0 and 10OH- 4018:0) were observed, providing clear evidence for the microbial degradation of bone organic matter 41and an input of lipids from specialised bacteria. Catalytic hydropyrolysis (HyPy) of demineralised extrac- 42tion residues released up to 0.13% of the total n-C16 and n-C18 moieties in the degraded bones. This 43revealed that only a small, yet sizeable portion of bone-derived fatty acyl units was sequestered into 44(proto)kerogen during the earliest stages of degradation.