Hinlopoceras Kröger & Pohle 2021, gen. nov.

• Main Authors: Kröger, Björn, Pohle, Alexander
• Format: Text
• Language: unknown
• Published: Zenodo 2021
• Subjects: Biodiversity; Taxonomy; Animalia; Mollusca; Cephalopoda; Tetrabranchia; Rioceratidae; Hinlopoceras; Ny Friesland; Svalbard; Hinlopen Strait; Spitsbergen
• Online Access: https://dx.doi.org/10.5281/zenodo.5793486; https://zenodo.org/record/5793486

Genus Hinlopoceras gen. nov. urn:lsid:zoobank.org:act: 1B85F4BE-F04C-4D03-A909-29003ACF507B Type species Hinlopoceras tempestatis gen. et sp. nov. from Olenidsletta Member, V1a trilobite zone, Blackhillsian, Floian. Diagnosis Longicones with slightly curved endogastric curvature during early ontogeny and orthoconic growth during later ontogeny, with cross section changing from circular in juvenile to compressed in adult growth stages; angle of expansion decreases during growth from ca 14° to 10°; ornamented with distinct transverse growth lines and striae; weak transverse annuli occur during latest growth stages; approximately four chambers occur at a distance similar to the corresponding conch height; siphuncle narrow with diameter ca ⅛ of corresponding conch height, strictly marginally positioned, with slightly concave segments and loxochoanitic septal necks. Etymology Referring to Hinlopen Strait, Svalbard, the type region of this genus. Comparison The new genus is unique within the Rioceratidae in having a combination of a relatively large angle of expansion, wide septal spacing, and a distinct transversely lirate ornamentation. The internal characters of this genus are relatively poorly known, because most specimens available have a strongly recrystallized phragmocone. The thin marginal siphuncle is nearly tubular or only very slightly concave, which can best be compared with that of Svalbardoceras gen. nov. The consistently poor preservation of the internal shell of specimens of Hinlopoceras gen. nov. in beds where internal features of Svalbardoceras gen. nov. are better preserved indicates that the septa were originally more fragile and sensitive to early dissolution and/or implosion. Species of Hinlopoceras gen. nov. can be distinguished from species of Svalbardoceras gen. nov. by their distinct ornamentation; in Hinlopoceras gen. nov. the conch is ornamented with transverse bands or striae, in Svalbardoceras gen. nov. the ornament consists of fine irregularly spaced growth lines. : 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 pages 23-24, DOI: 10.5852/ejt.2021.783.1601, http://zenodo.org/record/5793422 : {"references": ["Aubrechtova M. 2015. A revision of the Ordovician cephalopod Bactrites sandbergeri Barrande: systematic position and palaeobiogeography of Bactroceras. Geobios 48: 193 - 211. https: // doi. org / 10.1016 / j. geobios. 2015.03.002"]}