Fourier transform infrared characterization of the M iddle D evonian non‐vascular plant S pongiophyton

Spectroscopy information (functional groups and semiquantitative data) by F ourier transform infrared ( FTIR ) spectroscopy of S pongiophyton K räusel emend. C haloner et al . is reported for the first time, in an attempt to identify spectroscopic patterns that would differentiate species of these taxa. A total of 33 specimens identified as S . lenticularis , S . nanum and S . minutissimum and preserved as compressions were analysed. They come from the same fossiliferous horizon of one outcrop situated in the uppermost M iddle D evonian S ão D omingos F ormation of the P araná B asin in southern B razil. The results reveal that functional groups in the 3000–2800 and 1800–700 cm −1 wavenumber regions are present in all specimens. Infrared‐derived ratios ( CH 2 / CH 3 , A l/ O x, O x1/ O x2, C = O cont., C = C cont., A l2 and A r/ A l) and types of kerogen led to a comparison of the morphological characteristics of the studied material and indicate that compressions of S . lenticularis , S . nanum and S . minutissimum contain different organic compounds. S . nanum and S . minutissimum show higher oxidation and lower aromaticity of its organic matter than S . lenticularis . Additionally, S . lenticularis shows low A‐factor values, suggesting a composition similar to type III kerogen, while S . nanum and S . minutissimum showed intermediate to high A‐factor values, suggesting a composition similar to type II kerogen. In conclusion, the chemical‐analytical techniques and statistical analysis (using PCA technique) reveal a closer taxonomic relationship between S . nanum and S . minutissimum than either has with S . lenticularis , supporting their taxonomic separation, previously proposed in the literature on the basis of morphological features. Lastly, the chemical signatures support the hypothesis that links these enigmatic fossils to a type of lichen or other early inland plant.