Summary: | Fig. 29. Median sections of phragmocones of Bactroceras Holm, 1898. A, C–D. Bactroceras fluvii sp. nov., from Profilbekken river basin, locality PR-phosphatic. A. Specimen FMNH-P30159, with adapical siphuncular segment, taphonomically slightly distorted.B. Bactroceras boliviensis Aubrechtová, 2015, FMNH-P30176 from bed PO 131, extreme apical part. C–D. Specimen FMNH-P30177, holotype. C. Details of the protoconch. D. Apical part with transition toward juvenile growth stages; note the slightly expanded siphuncular segments. Scale bars: A = 5 mm; B–C = 1 mm; D = 2 mm. Published as part of Kröger, Björn & Pohle, Alexander, 2021, Early-Middle Ordovician cephalopods from Ny Friesland, Spitsbergen - a pelagic fauna with Laurentian affinities, pp. 1-102 in European Journal of Taxonomy 783 (1) on page 41, DOI:10.5852/ejt.2021.783.1601, http://zenodo.org/record/5793422
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