CHEMICAL CHARACTERIZATION OF CYCADOLEPIS SCALE-LEAVES FROM THE SPRINGHILL FORMATION (LOWER CRETACEOUS, ARGENTINA)

LAFUENTE DIAZ, MAITEN; DEL FUEYO GEORGINA M.; D'ANGELO, JOSÉ A.; CARRIZO MARTIN A.

Otro; 1° Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina; 2020

Scale-leaves of Cycadolepis spp. (Bennettitales) are analyzed for the first time byFourier Transform Infrared (FTIR) spectroscopy revealing mesophyll and cuticle preservedfunctional groups. The latter are used to characterize five potential specieswith the aim of evaluating the functional groups as potential chemotaxonomicparameters. The material consists of five incompletescale-leaf compressions with well-preserved cuticles (MPM-PB 15341-15345), fromthe Springhill Formation (Hauterivian-Barremian; Santa Cruz, Argentina). For thespectrometric study, scale-leaves were analyzed into two sample forms:compressions (including coalifiedmesophyll and cuticle) and cuticles. In turn, one specimen wasdifferentiated into apical and basal parts (MPM-PB 15343). Semi-quantitative IR-datawere evaluated using principal component analysis. The resultsindicate that compressions have a similar chemical composition among specimensand scale parts with a low contribution of aromatic carbon compounds. Incontrast, the cuticles show high variability. Particularly, the variation of oxygen-containingcompounds could be due to the chemical composition of cutin/cutan and otherconstitutive compounds of the cuticle. Additionally, the presence of diversetrichomes (hairs, papillae, and idioblasts) could contribute to the variabilityof the cuticle sample form. On the other hand, no distinctive differences amongthe specimens were recognized. In this case, the intraspecific variabilityamong the specimens, which is denoted in cuticular features, could hamper theuse of functional groups as additional taxonomic parameters to thosemorphoanatomical. Although preliminary, these results areencouraging and contribute to a better understanding of the chemical composition of five Patagonian species of Cycadolepis,a genus known by its peculiar variability.