Fig. 4 in A microanatomical and histological study of the postcranial dermal skeleton in the Devonian sarcopterygian Eusthenopteron foordi

Fig. 4. Scale ultrastructure of the sarcopterygian Eusthenopteron foordi Whiteaves, 1881 (MNHM 06−615A) from the Late Devonian, Escumenac Bay, Quebec, Canada. A. Transmitted natural light, semi−thin section. Toluidine blue staining showing three vertically−sectioned scales. The organic matrix is stained in the external layer; in the basal plate, the mineral remnants are black (arrow). B. Nomarski interference optical micrograph. Semi−thin vertical section of a demineralised scale. Fractures are abundant, but the general organisation of the scale is still preserved. C. Transmitted natural light, semi−thin section, toluidine blue staining. Detail of the outer layer where a fuzzy material forms intensively stained stratified lines (arrow). D. Nomarski interference optical micrograph. Semi−thin vertical section. The surface of the basal plate shows parallel ripples. Micro−organisms, probably bacteria, are attached to the side of the basal plate (arrow). E. TEM. Demineralised basal plate of scale. The closely packed fibrils, roughly oriented in the same direction, are connected by bridges. F. TEM. Basal plate. Detail showing the regularly spaced bridges connecting two adjacent fibrils (arrows). G. TEM. Partially demineralised scale. Regularly distributed mineral crystals remain attached to the fibrils (arrowheads). Some fibrils show a discernible periodic structure (arrows). Abbreviations: bp, basal plate; el, external section.