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Chemistry of fossil cynodont bones from Early Triassic of Argentina



From: Ben Creisler
bcreisler@gmail.com



A recent non-dino paper:


Elena Previtera, José A. D'Angelo, Adriana C. Mancuso (2013)
Preliminary chemometric study of bone diagenesis in Early Triassic
cynodonts from Mendoza, Argentina.
Ameghiniana 50(4) : 460 – 468
http://www.ameghiniana.org.ar/index.php/ameghiniana/article/view/623




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.