Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs

Abstract

Dutta, S., Hartkopf‐Fröder, C., Mann, U., Wilkes, H., Brocke, R. & Bertram, N. 2010: Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs. Lethaia, Vol. 43, pp. 334–343. Biogeochemistry and molecular taphonomy of biopolymers of marine zoomorphs are poorly known. In order to obtain insights into this issue we report on the biogeomacromolecular composition of hand‐picked, well‐preserved scolecodonts of Ordovician, Silurian and Devonian age using micro‐Fourier transform infrared (micro‐FTIR) spectroscopy, Curie point pyrolysis‐gas chromatography‐mass spectrometry (Cupy‐GC‐MS) and tetramethylammonium hydroxide (TMAH)‐assisted thermochemolysis‐GC‐MS. The present study reveals that scolecodonts are composed of both aliphatic and aromatic moieties. The micro‐FTIR spectra of scolecodonts are characterized by aliphatic CHx (3000–2800 and 1460–1450/cm) and CH3 (1375/cm) absorptions and aromatic C=C (1560–1610/cm) and CH (3050/cm and 700–900/cm) absorptions. The major pyrolysis products from the scolecodonts include aromatic hydrocarbons such as alkylbenzenes, alkylnaphthalenes and alkylphenols. Aliphatic hydrocarbons are represented by a homologous series of n‐alkenes and n‐alkanes. The compounds released upon thermochemolysis with TMAH are saturated and unsaturated fatty acids (as their methyl esters), n‐alkenes/alkanes and aromatic acids (as their methyl esters). No protein/amino acid‐derived compounds have been recognized in the pyrolysates or in the thermochemolysates, and it is concluded that protein/amino acid‐related compounds, which are commonly found in the jaws of extant polychaetes, were destroyed due to diagenetic processes. Obviously, excellent morphological preservation and low thermal alteration are not paralleled by a similar degree of chemical preservation. □Biogeomacromolecules, micro‐FTIR, pyrolysis‐GC‐MS, scolecodonts, thermochemolysis‐GC‐MS.

Chemical preservation of tail feathers fromAnchiornis huxleyi, a theropod dinosaur from the Tiaojishan Formation (Upper Jurassic, China)

“…) and Palaeozoic annelid fossils (Dutta et al . ). However, even if no proteinaceous compounds were detected in Anchiornis feathers, one cannot exclude the possibility of finding similar biomolecules preserved in other fossils in the future.…”

Fossilization of melanosomes via sulfurization

“…Hopanoid producing microbes are predominantly aerobic; abundant hopane moieties in other fossil vertebrate soft tissues has been interpreted as evidence of extended decay in aerobic conditions (Edwards et al . ). The lack of hopane moieties in the Libros frog tissues could indicate predominantly anaerobic decay before and after deposition.…”

Optical thermal maturity parameters and organic geochemical alteration at low grade diagenesis to anchimetamorphism: A review

“…copper, iron, zinc) are particularly highly concentrated in the tips (e.g. Eriksson and Elfman, 2000;Jeuniaux, 1963;Lichtenegger et al, 2002;Voss-Foucart et al, 1973; for more references on modern polychaete jaw chemistry see Dutta et al, 2010). Scolecodonts, the fossilized jaw elements, can presumably be classified as Type III kerogen (Tyson, 1995) and also have metal enrichments in areas which had been more exposed to abrasion in the living animal (Eriksson and Elfman, 2000).…”

“…a homologous series of n-alkenes and n-alkanes). No protein/amino acid derived compounds have been recognized which is attributed to diagenetic alteration (Dutta et al, 2010). Gupta and Briggs (2011, p. 205) found a dominant aromatic composition in scolecodonts from the Upper Ordovician of Cincinnati but no thermal maturity data are provided.…”

“…The application of acetic acid, bleach and mineral spirit solution as used in the sample preparation by Nowaczewski (2011) and Olcott Marshall et al (2013) may be problematic as it is unknown whether these reagents have effects on the chemical composition of palynomorphs. Oxidizing agents in particular should always be avoided while the commonly applied hydrochloric/hydrofluoric acid digestion as employed by Dutta et al (2010Dutta et al ( , 2013 is not thought to significantly influence the chemical composition of fossil organic material as long as it is not very immature (for further discussion see van Bergen, 1999).…”