Comments on “Dental lessons from past to present: ultrastructure and composition of teeth from plesiosaurs, dinosaurs, extinct and recent sharks” by A. Lübke, J. Enax, K. Loza, O. Prymak, P. Gaengler, H.-O. Fabritius, D. Raabe and M. Epple, RSC Adv., 2015,5, 61612

Abstract

Comments on "Dental lessons from past to present: ultrastructure and composition of teeth from plesiosaurs, dinosaurs, extinct and recent sharks"The paper mentioned in the title suggests that several groups of extinct vertebrates used fluoroapatite as a tooth mineral in dentine and enamel when alive; its authors posit that this tooth mineralization drastically changed in all these lineages at some point during their evolution, leading to the use of hydroxyapatite as an alternative primary tooth mineral, because of hitherto unconsidered environmental changes. These conclusions are based on their finding high fluoride levels (i.e. fluoroapatite) in the dentine of fossilised shark teeth as well as in both the dentine and enamel of plesiosaurs, mosasaurs, and dinosaurs, which is in sharp contrast to recent teeth (which contain almost no fluoride in the dentin or enamel; i.e. hydroxyapatite). However, in our opinion, the authors have either obviated or underestimated a process well known to palaeontologists and archaeologists: the fluorine content of fossil teeth and bones increases with age during the course of fossilization because of the diagenetic passage of hydroxyapatite to more stable fluoroapatite. Thus, the aim of this letter is to show that the high fluoride contents found in the questioned paper are due to the diagenetic alteration of fossils, with the goal of avoiding future confusion.The mineralised tissues (bone, dentine and enamel/oid) that form the skeletal elements of vertebrates (bones, teeth, spines, dermal denticles, etc.) comprise an organic matrix and

Micro-computed tomography imaging reveals the development of a unique tooth mineralization pattern in mackerel sharks (Chondrichthyes; Lamniformes) in deep time

“…In extant sharks, enameloid has a much higher degree of crystallinity and a very low organic content compared to dentine 62,63 , which makes it appear denser in micro-CT images 26,34 . The poor results for fossil teeth can be distorted by diagenetic processes leading to changes in the chemical constitution of enameloid 63,68 resulting in less differences of densities between enameloid and dentine. Nonetheless, in most cases micro-CT scanning generated images that sufficiently resolved the internal structures of both, extant and fossil shark teeth without damaging or destroying the material and therefore, should be regarded as a reliable non-invasive alternative to conventional thin sectioning.…”

Reply to the ‘Comments on “Dental lessons from past to present: ultrastructure and composition of teeth from plesiosaurs, dinosaurs, extinct and recent sharks”’ by H. Botella et al., RSC Adv., 2016, 6, 74384–74388

“…12-14 and also the article by de Renzi et al 11 ). This means that no conclusion is possible for fossil samples with respect to their original uoride content.…”

Structural, chemical and isotope evidence for secondary phosphate mineralization of grasping spines of Early Palaeozoic chaetognaths

“…5C) may, in turn, point to its primary or very early diagenetic origin as fluoride content increases during late diagenetic transformation of bioapatites (de Renzi et al . 2016; Luebke et al . 2017).…”