Fig. 5

Bone histology of Saurichthys opercle PIMUZ T 2566. Images a, c1, d1 in normal transmitted, c2, d2 in cross-polarized and b, c3, d3 in cross-polarized light using lambda compensator. a, b Cross section of whole opercle (anterior towards the right of image). Position of close-ups shown in b and c are indicated by red squares; c1–c3 close-up of flat posterior part of opercle. Note that tips of ornamental ridges (indicated by black and white asterisks in c1 and c2) were separated from the rest of the opercle during thin-sectioning; d1–d3 close-up of anterior articulation part of opercle. Note Sharpey’s fibers inserting internally into the bone matrix. Growth marks (annuli/LAGs between growth zones) are visible throughout the bone tissue as indicated by black or white arrow heads in c and d. GM growth marks, LP lamellate part of opercle, ORP ornamented part of opercle, PFB parallel-fibered bone, ShF Sharpey’s fibers