Fossil cutin of Macroneuropteris scheuchzeri (Late Pennsylvanian seed fern, Canada)

Abstract

Cutin polymer from compression-preserved specimens of Macroneuropteris scheuchzeri (seed fern, Medullosales) is recorded for the first time. Specimens of basal Cantabrian strata, Sydney Coalfield, Canada, exhibit excellent preservation. The cutin was concentrated by Schulze's process by time-controlled oxidation reaction. Reported are functional-group changes monitored via semi-quantitative Fourier transform infrared (FTIR) spectrometry as a function of cutin concentration in Schulze's solution. Distinct features of the cutin spectrum include intense peaks of ester CO groups, centered at 1730–1715cm−1, and aromatic CC absorption bands at 1640–1645cm−1. Cutin is characterized and differentiated from the corresponding M. scheuchzeri cuticle mainly by the comparatively higher values of CH2/CH3, CO/CC, and the very low values of CHal/CO and CC contribution. Cutin data compare with available semi-quantitative FTIR data from modern L. esculentum cutin, particularly emphasized by CHal/CO ratios whose low value of ca. 0.9 indicates a similar cross-linking degree of the polymeric structure for the fossil and extant taxa.