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Swiss Journal of Palaeontology
Fig. 6 | Swiss Journal of Palaeontology

Fig. 6

From: Siphonal tube structure of the Late Devonian orthocerid Dolorthoceras from the Polar Urals (NW Russia) preserving nacre and organic fibres as well as its persistence in cephalopod evolution

Fig. 6

Dolorthoceras sp. (PIN-1894/100); River Malaya Usa, Polar Urals, NW Russia; Frasnian, Late Devonian. Median conch section. a The ultrastructural difference between the columnar-nacreous septal neck and the fibrous lens-shaped structure (sectioned clutch) coating the posterior part of the septal neck. Note that the thin connecting ring is adjacent to the outer surface of the clutch. Scale bar is 0.1 mm. b Enlarged detail of A to show the fibrous ultrastructure of the lens-like structure (sectioned clutch). Scale bar is 30 µm. ch chamber, cr connecting ring, ls lens-shaped structure, s septum, siph siphuncle, sn septal neck

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