Preliminary Chemometric Study of Bone Diagenesis in Early Triassic Cynodonts from Mendoza, Argentina

Abstract

The non-mammalian therapsids dominated the terrestrial ecosystems during the Late Paleozoic-Early Mesozoic. The cynodonts have been studied from a taxonomic, osteologic and morphological perspective. However, taphonomy using chemometrics has been barely explored. This report includes a rib and an appendicular bone of cynodonts from the Puesto Viejo Group (Mendoza, Argentina). These fossils are studied for the first time using SEM-EDX. Semi-quantitative data derived from SEM-EDX spectra is evaluated by principal component analysis to gain new insights regarding the different diagenetic pathways of bone microstructure. The multivariate model supports the distinction of different sampled areas (bone, transition zone and rock matrix), in terms of chemical parameters. Differentiation is based mainly on varying contents of Ca, P, F, Si, Al, K, O, Mn and Fe. Variable concentrations of Fe and Mn could be related to different facies (floodplain and crevasse splay). These results along with thin section petrographical analysis confirm -in one of the cases-the substitution of hydroxyapatite by fluorapatite in the bone microstructure. Fossil-diagenetic processes observed herein include substitution, fracturing, brittle deformation and different permineralization events. Permineralization stages during burial history include infilling of vascular canals, trabeculae and fractures with hematite, manganite and calcite. The presence of calcite and iron enrichment indicates local reducing conditions below water-table during precipitation. This chemometric approach to the study of Triassic cynodont remains proved useful for assessing the chemical changes in bone microstructure.

A Late Cretaceous mammal from Brazil and the first radioisotopic age for the Bauru Group

“…The results of the elemental analyses (electronic supplementary material, figure S3) are similar to those of previous studies on fossil bones and teeth from several fossil sites [27,28]. The major elements include oxygen (35.6 wt%), calcium (29.6 wt%) and phosphorus (10.2 wt%).…”

Chemical taphonomy and preservation modes of Jurassic spinicaudatans from Patagonia: a chemometric approach

“…The use of semiquantitative EDS analysis to study fossil materials has been demonstrated to be reliable and has provided reproducible results (e.g., Klug et al, 2009; Lin and Briggs, 2010; Thomas et al, 2012; Previtera et al, 2013; Benavente et al, 2014). The absolute method (as opposed to a relative method) used here does not employ standards (e.g., Vázquez et al, 1988, 1990; Barrea and Mainardi, 1998; D’Angelo et al, 2002).…”

Plant Taphonomy in a Lake Affected by Volcanism (Agua De La Zorra Formation, Upper Triassic) Mendoza, Argentina

“…The chemometric approach conducted using a Scanning Electron Microscope (SEM) in combination with energy-dispersive X-ray spectrometry (EDX) has proved to be useful in providing diagenetic information related to different modes of preservation of fossil remains (e.g., Previtera et al 2013;Benavente et al 2014;Monferran et al 2018;Previtera 2019). Although the results provided by the standard procedure are qualitative and semiquantitative, SEM-EDX allows the determination of major and minor components of different materials.…”