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

Microscope, cathodoluminescence, chemical and oxygen isotope studies have been conducted to determine the original mineralogy diagenetic alteration of phosphatic grasping spines Cambrian chaetognaths. The obtained data, along with a comparison composition conodont apatite, show presence few generations phosphate phases. A thin, outer layer is composed very early phosphate, which incrusted cuticle contributing preservation an shape structural details fossils. This process can be linked ‘Orsten’-type phosphatization mainly known from Lower Palaeozoic strata. Successive are observed within middle inner layers as well internal cavities spines. Plastic deformations features that they were originally slightly flexible chitinous organic matter similar modern conclusion substantiated by rare findings purely remnants chaetognath