INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Diagenetic analysis of therapsid bones from the Upper Triassic (Puesto Viejo Group), Mendoza, Argentina
DE LA FUENTE, M. S.; MANCUSO, A.; PREVITERA, E.
Congreso; 11° Congreso de la Asociación Paleontológica Argentina; 2016
Uniiversidad Nacional de Río Negro
Non-mammalian therapsids dominated in terrestrial ecosystems during the late Paleozoic andearly Mesozoic. Although cynodonts and dicynodonts have been studied from severalperspectives, the relation between the specimens and their sedimentary context has beenscarcely documented. This study is aimed to elucidate bone diagenesis in therapsids inparticular for specimens collected from the Late Triassic Puesto Viejo Group (Mendoza,Argentina). Bone histology and diagenetic features were analyzed through thin sections tointerpret the degree of taphonomic alteration. The studied materials correspond to ribs andappendicular bones of cynodonts (MHNSR-PV 1159; 1160; 1162; 1164) and dicynodonts(MHNSR-PV 1161; 1163). Particularly, bones of Diademodon tetragonus Seeley, 1894(MHNSR-Pv 1164) from the Museo de San Rafael (Mendoza) collection were also studyalthought, information about their sedimentary context was not available. This sample wasused to test the utility of our diagenetic approach to identify the facies context (depositionalframework) where the specimen was buried. Histological examination revealed apredominance of fibrolamellar tissue, intense Haversian remodeling and growth marks, thussuggesting adult individuals. Diagenetic processes inferred include substitution, fracturing,deformation, and different permineralization stages of iron carbonate minerals. Combinedanalyses including scanning electron microscopy (SEM-EDX), X-ray diffractometry (XRD)and petrography reveal the substitution of hydroxyapatite by francolite in the bonemicrostructure. The presence of fluoride-bearing apatite in therapsid bones is an indicator ofdiagenetic ion exchange through interaction with ground water, therefore, suggests a closelink between the elemental composition and the depositional environment. *Study supported by PICT 2013-0095 to M.S.F and PICT 2013-0805 to A.C.M.