Fossildiagenesis and ontogenetic insights of crocodyliform bones from the Adamantina Formation, Bauru Basin, Brazil. (December 2019)

• Record Type: Journal Article
• Authors: Marchetti, Isadora; Ricardi-Branco, Fresia; Callefo, Flavia; Delcourt, Rafael; Galante, Douglas; Jurigan, Isabela; Carvalho, Ismar S.; Tavares, Sandra A.S.
• Is Part Of: Journal of South American earth sciences. Volume 96(2019)
• Publication Date: 2019-12
• Subjects: Paleohistology -- REEs -- Cretaceous -- Crocodile -- Montealtosuchus; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2019.102327
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: The histological analysis of fossil bones allows a taphonomic approach, especially to fossildiagenesis. We studied the femur, vertebra, and osteoderm of the crocodyliform Montealtosuchus arrudacamposi (Adamantina Formation; Late Cretaceous), to make inferences of the sequence of the diagenetic processes. Cross-sections of the bones and the rock matrix that fills the medullar cavity were analyzed under a scanning electron microscopy with compositional analysis (SEM/EDS) and μ-X-Ray fluorescence (μ-XRF). The microstructural pattern of the femur and vertebra was similar, with a transition from vascularized fibrolamellar internal cortex, with reticular and longitudinal canals to zonal lamellar in the outer, and a medullary cavity portion filled with quartz and other mineral grains. The osteoderm, however, presented a less vascularized cortex. In all samples were found the External Fundamental System (EFS), secondary osteons in the internal cortex and spongy tissue, and the transition from a fibrolamellar to a lamellar tissues, indicating that the individual reached ontogenetic maturity (adult/senescent) before they died. The compositional results showed that the samples mainly comprised calcium and phosphorus, which were homogeneously distributed. However, we inferred that these elements occurred during the formation of recrystallized and authigenic minerals. Iron, vanadium, and cerium are the elements found that occurred in the composition of the fossil remains during early diagenesis, and this process was observed to extend to the late diagenesis. Cerium was homogeneously distributed and incorporated to authigenic apatite. Iron and vanadium were restricted to the cortex. The presence of authigenic apatite and Rare Earth Elements (REEs) in the samples supported that the diagenetic environment of the Adamantina Formation was alkaline. Furthermore, it suggested an association with a groundwater environment that have allowed and facilitated the well preservation of fossil vertebrates in this geological formation. Graphical abstract: Image 1 Highlights: Histological analysis of Montealtosuchus allows to understand their fossildiagenesis. The histological samples of Montealtosuchus were analyzed with SEM/EDS and μ-XRF. The Montealtosuchus fossils bones are in majority composed by calcium and phosphorus. Iron, vanadium and cerium were incorporated in the bones of Montealtosuchus during eodiagenesis.