Preservation of uropygial gland lipids in a 48-million-year-old bird

Although various kinds of organic molecules are known to occur in fossils and rocks, most soft tissue preservation in animals is attributed to melanin or porphyrins. Lipids are particularly stable over time—as diagenetically altered ‘geolipids’ or as major molecular constituents of kerogen or fossil ‘geopolymers’—and may be expected to be preserved in certain vertebrate tissues. Here we analysed lipid residues from the uropygial gland of an early Eocene bird using pyrolysis gas chromatography mass spectroscopy. We found a pattern of aliphatic molecules in the fossil gland that was distinct from the host oil shale sediment matrix and from feathers of the same fossil. The fossil gland contained abundant n-alkenes, n-alkanes and alkylbenzenes with chain lengths greater than 20, as well as functionalized long-chain aldehydes, ketones, alkylnitriles and alkylthiophenes that were not detected in host sediment or fossil feathers. By comparison with modern bird uropygial gland wax esters, we sh...

尽管已知化石和岩石中存在多种有机分子，但动物软组织的保存大多归因于黑色素（melanin）或卟啉（porphyrins）。脂质随时间推移具有特别的稳定性——无论是作为成岩作用改变后的“地质脂质（geolipids）”，还是作为干酪根（kerogen）或化石“地质聚合物（geopolymers）”的主要分子成分——因此有望在某些脊椎动物组织中保存下来。本研究采用热解气相色谱-质谱联用技术（pyrolysis gas chromatography mass spectroscopy）分析了早始新世鸟类尾脂腺（uropygial gland）中的脂质残留物。我们在该化石尾脂腺中发现了一种脂肪族分子模式，其与宿主油页岩沉积基质以及同一化石的羽毛中的分子模式均存在显著差异。该化石尾脂腺中含有丰富的链长大于20的正烯烃（n-alkenes）、正烷烃（n-alkanes）和烷基苯（alkylbenzenes），以及功能化长链醛、酮、烷基腈（alkylnitriles）和烷基噻吩（alkylthiophenes）——这些物质在宿主沉积物或化石羽毛中均未检测到。通过与现代鸟类尾脂腺蜡酯的对比，我们...