Chemical diversity of cretaceous plant fossils from Patagonia: implications for taphonomy and chemotaxonomy (Santa Cruz province, Argentina

LAFUENTE DIAZ, MAITEN A.; DEL FUEYO, GEORGINA M.; D`ANGELO J A; CARRIZO, MARTÍN A.

Congreso; XII Congreso de la Asociación Paleontológica Argentina; 2021

Fourier Transform Infrared (FTIR) spectroscopy allows revealing information on the chemical diversity of plant fossils. Thus, several Gymnosperm fossil remains, collected from Cretaceous geological units outcropping in the Santa Cruz province (Argentina), were spectroscopically analyzed. Particularly, fossil taxa include the conifer Squamastrobus tigrensis (BA Pb 7678, 11321, 11324, 11333), the cycadal Pseudoctenis ornata (BA Pb 1217, 1220, 1222), and the ginkgoal Ginkgoites tigrensis (BA Pb 11556, 11557, 11561, 14880, 14883, 14887-14889) from the Baqueró Group (Aptian), the bennettitalean Ptilophyllum micropapillosum (MPM Pb 15355) and Cycadolepis spp. (MPM Pb 15341-15345) and the pteridosperma Ruflorinia orlandoi (MPM Pb 15313, 15323-15330, 15333) from the Springhill Formation (Hauterivian-Barremian), and the ginkgoal Ginkgoites skottsbergii (BA Pb 13850) from the Piedra Clavada/Kachaike Formation (Albian). Specimens are preserved as compressions and cuticles and are characterized through semi-quantitative FTIR analysis followed by multivariate statistical evaluation (PCA).Results indicate little intra- and interspecific variability. The former is mainly related to morphological?? cuticular features and biomacropolymeric chemistry, whereas the latter to leaf types and plant groups´ particularities. Despite the relevant chemical information, spectroscopic patterns characterizing each fossil taxon are not always chemotaxonomically distinctive. Additionally, similarities among species from the same lithostratigraphic unit are recorded. Is it possible that taphonomic processes give fossil remains a specific ?fingerprint? of the fossiliferous locality? Because functional groups are related to structures common to all plants (structural compounds and primary and secondary metabolites), to achieve an integral knowledge of the specimens is necessary a multidisciplinary approach.