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Swiss Journal of Palaeontology
Fig. 4 | Swiss Journal of Palaeontology

Fig. 4

From: An assessment of age determination in fossil fish: the case of the opercula in the Mesozoic actinopterygian Saurichthys

Fig. 4

Bone histology of outgroup taxa Polypterus bichir (a–c), Lepisosteus cf. L. oculatus (d–g) and Acipenser baerii (h–k). All images in normal transmitted light except f in cross-polarized light using lambda compensator and j in cross-polarized light. a Complete section of opercle (NMB 2793); b close-up of external bone surface ornamentation showing ganoine of the odontodes; c close-up of posterior part of opercle showing two successive growth marks in the bone tissue (white arrow heads); d complete section of opercle (PIMUZ A/I 4170); e complete section of subopercle (PIMUZ A/I 4170); f close-up of posterior part of opercle showing seven successive growth marks (white arrow heads); g close-up of canaliculi (canals) of Williamson (black arrow heads) and external ornamentation with ganoine ridges; h complete section of subopercle of 6-year-old female specimen (PIMUZ A/I 4310); i complete section of subopercle of 3-year-old female specimen (PIMUZ A/I 4308); j close-up of posterior part of subopercle (PIMUZ A/I 4310) showing two successive growth marks in the bone tissue (white arrow heads); k close-up of a more anterior section of the subopercle (PIMUZ A/I 4310) showing six successive growth marks as dark growth zones and bright annuli (white arrow heads) in the basal (visceral) part of the bone

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