New Insights in the Ontogeny and Taphonomy of the Devonian Acanthodian Triazeugacanthus affinis From the Miguasha Fossil-Lagerstätte, Eastern Canada

Abstract

Progressive biomineralization of a skeleton occurs during ontogeny in most animals. In fishes, larvae are poorly mineralized, whereas juveniles and adults display a progressively more biomineralized skeleton. Fossil remains primarily consist of adult specimens because the fossilization of poorly-mineralized larvae and juveniles necessitates exceptional conditions. The Miguasha Fossil-Lagerstätte is renowned for its Late Devonian vertebrate fauna, revealing the exceptional preservation of fossilized ontogenies for 14 of the 20 fish species from this locality. The mineralization of anatomical structures of the acanthodian Triazeugacanthus affinis from Miguasha are compared among larval, juvenile and adult specimens using Energy Dispersive X-ray Spectrometry. Chemical composition of anatomical structures of Triazeugacanthus reveals differences between cartilage and bone. Although the histology and anatomy is well-preserved, Fourier transform infrared spectrometry shows that the original chemical composition of bone is altered by diagenesis; the mineral phase of the bone (i.e., hydroxyapatite) is modified chemically to form more stable carbonate-fluorapatite. Fluorination occurring in mineralized skeletal structures of adult Triazeugacanthus is indicative of exchanges between groundwater and skeleton at burial, whereas the preservation of larval soft tissues is likely owing to a rapid burial under anoxic conditions. The exceptional state of preservation of a fossilized ontogeny allowed us to characterize chemically the progressive mineralization of the skeleton in a Devonian early vertebrate.

Two types of bone necrosis in the Middle TriassicPistosaurus longaevusbones: the results of integrated studies

“…Infrared analysis of hydroxyl region (3800–2800 cm −1 ) showed predominant contribution of OH − groups. In the non-altered fossil bone only a water signal, typically observed in fossilized bone apatite [ 52 ], was detected ( figure 3 g , h ). Hence, higher incorporation of hydroxyl moieties into the apatite-like phase structures correlates with an increase of structural distortion in pathological bone.…”

Atomic scale transformation of bone in controlled aqueous alteration experiments

“…Furthermore, the study of bone diagenetic processes has wide implications, e.g. in archaeological contexts where preservation assessment of bones is key to bone collagen dating (Lebon et al, 2016) and in oceanic environments where biomineralised tissues of Devonian fish shed light on their ontogeny and taphonomy (Chevrinais et al, 2015).…”

Modeling the attenuated total reflectance infrared (ATR-FTIR) spectrum of apatite

“…The other type of information is related to the concentration and location of molecular species, such as carbonate groups, that are detected by specific vibrational bands (e.g. Michel et al 1995;Fleet and Liu 2008;Fleet 2009;Yi et al 2014;Chevrinais et al 2016). Although the majority of infrared spectroscopic studies of apatite were performed using transmission experiments, recent investigations have used ATR spectroscopy to unravel the modification of biologic apatite during fossilization (e.g.…”