Chemotaxonomic comparison of the seed ferns Odontopteris cantabrica and Odontopteris schlotheimii, Middle Pennsylvanian Sydney Coalfield, Canada

Abstract

We present the first comparative spectrochemical data in the study history of Odontopteris schlotheimii Brongniart, 1828–1831 and Odontopteris cantabrica Wagner, 1969. These fossils co-occur in the shaley roof of the Lloyd Cove seam (Ro% = 0.65; Sydney Coalfield, Canada). Fourier transform-infrared spectra show that the sampled pinnules of both species are preserved as fossilized-cuticles. They are prominently aliphatic with distinct methylene and methyl peaks (at 2922 cm–1 and 2852 cm–1); with relatively high contents of carbonyl groups (peaks at 1700 cm–1) that indicate a high degree of molecular cross linking; and with smaller amounts of aromatics (peaks at 820 cm–1 and 750 cm–1) with a low condensation degree of benzene rings. No differences among respective pinnules are inferred from the 3D chemometric model and associate significance tests by the analysis of variance (α = 0.05). At the same time, this method provides new, chemical parameters that, in conjunction with morphological features, could be used to efficiently distinguish species.