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, JOSÉ A.; CARRIZO MARTIN A.

Congreso; XII Congreso de la Asociación Paleontológica Argentina; 2021

APA

Fourier Transform Infrared 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. The materials are deposited in the Colección Paleobotánica del Museo Argentino de Ciencias Naturales ?Bernardino Rivadavia? (BA Pb) and the Museo Regional Padre M.J. Molina (MPM Pb).Particularly, fossil taxa include the conifer Squamastrobus tigrensis (BA Pb 7678, 11321, 11324, 11333), the cycadalean Pseudoctenis ornata (BA Pb 1217, 1220, 1222), and the ginkgoalean Ginkgoites tigrensis (BA Pb 11556, 11557, 11561, 14880, 14883, 14887-14889) from the Baqueró Group (Aptian), the bennettitaleans Ptilophyllum micropapillosum (MPM Pb 15355) and Cycadolepis spp. (MPM Pb 15341-15345), and the pteridosperm Ruflorinia orlandoi (MPM Pb 15313, 15323-15330, 15333) from the Springhill Formation (Hauterivian?Barremian), and the ginkgoalean Ginkgoites skottsbergii (BA Pb 13850) from the Piedra Clavada/Kachaike Formation (Albian). Specimens consist of compressions with well-preserved cuticles which are characterized through semi-quantitative Fourier Transform Infrared analysis followed by multivariate statisticalevaluation (Principal Component Analysis). Results indicate little intra- and interspecific variability. The former is mainly related to morphological cuticular features and biomacropolymeric chemistry, whereas interspecific variability 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 samelithostratigraphic unit are recorded. Therefore, it is addressed the possibility that taphonomic processes give fossil remains a specific ?fingerprint? depending on the fossiliferous locality. Finally, it is highlighted the necessity of a multidisciplinary approach to achieve an integral knowledge of the specimens because functional groups are related to structures common to all plants (structural compounds and primary and secondary metabolites).