Svalbardoceras, Kröger & Pohle, 2021

Kröger, Björn & Pohle, Alexander, 2021, Early-Middle Ordovician cephalopods from Ny Friesland, Spitsbergen - a pelagic fauna with Laurentian affinities, European Journal of Taxonomy 783 (1), pp. 1-102 : 29-30

Genus Svalbardoceras gen. nov.

urn:lsid:zoobank.org:act:AE232B80-8CB8-45F8-A9BA-80620CD0D41C

Type species

Svalbardoceras sterna gen. et sp. nov.; Early Ordovician, late Floian, Olenidsletta Member, Valhallfonna Formation Öland, Spitsbergen.

Diagnosis

Weakly curved endogastric longicones with angle of expansion 5° to 7°; shell ornamented with shallow, irregularly spaced undulations, which are more pronounced in later growth stages, and with fine but distinct irregularly spaced directly transverse, imbricate growth lines; three to four chambers occur per distance similar to the corresponding conch cross section; thin marginal siphuncle with rSD ≈ ⅛ to ¹/6, siphuncle marginally, or nearly so, positioned at concave side of conch curvature; septal necks loxochoanitic to orthochoanitic; connecting ring relatively thick with slightly concave segments, almost tubular, endosiphuncular and cameral deposits not known.

Etymology

Referring to Svalbard, the type region of this genus.

Comparison

This new genus is unique within the Rioceratidae in having a combination of relatively wide septal spacing, a thin marginal siphuncle and an ornamentation with shallow, irregularly spaced undulations that are more pronounced in later growth stages. The similarly annulated and weakly curved Felinoceras Kröger & Evans, 2011 differs in having a narrower septal spacing and a distinctive annulation throughout

its growth. Semiannuloceras Evans, 2005 differs in possessing, in addition, a longitudinal ornamentation. The conch of Rioceras Flower, 1964 is smooth throughout its entire growth.