Olenidslettoceras farmi Kröger & Pohle 2021, gen. et sp. nov.
Creators
- 1. Finnish Museum of Natural History, University of Helsinki, PO Box 44, FI- 00014 Helsinki, Finland.
- 2. Paläontologisches Institut und Museum, University of Zurich, Zurich, Switzerland.
Description
Olenidslettoceras farmi gen. et sp. nov.
urn:lsid:zoobank.org:act: 8AE46041-CAE1-4ABB-8082-A21AD56CB9E5
Figs 5F–G, 6D, 8C, 50A
DiagnosisAs for genus, by monotypy.
EtymologyReferring to M/S Farm, the transport vessel of Henningsen Transport & Guiding A/S that brought the specimen back from Profilstranda to Longyearbyen; Spitsbergen.
Type materialHolotype Specimen FMNH-P30380.
Paratype One additional specimen, FMNH-P30345, from type horizon and locality.
Type locality and horizonFrom Profilstranda section, adjacent to Hinlopenstretet, Spitsbergen, bed PO 123.3, 120.3 m above base of Olenidsletta Member, V 2a trilobite zone, Blackhillsian, Floian
DescriptionThe holotype is a 47 mm long fragment of a phragmocone with part of the body chamber preserved (Fig. 5F–G). The conch is exogastrically curved, more so in the apical parts of the specimen. The preserved part of the body chamber is ca 15 mm long. The conch cross section is elliptically depressed, it grows in width from 9.5 mm to 14 mm and in height from 7.6 mm to 10.8 mm at a length of 36 mm
(expansion of width 7°, of height 5°, rW ≈1.3). The surface of the holotype is relatively poorly preserved but is presumed originally smooth, with weak growth lines.
The second specimen has a well-preserved conch surface and shows weak growth lines which run directly transverse and form a shallow and wide sinus at the antisiphuncular side of the conch. The second specimen is a fragment of a phragmocone, which grows in width from 8.7 to 11 mm and in height from 7.2 mm to 9.2 mm (expansion of width 11°, and height 9°) at a length of 13 mm. The corresponding rW is 1.21 and 1.19, respectively.
The chamber spacing is narrow, seven to ten chambers occur at a distance similar to the conch height. The siphuncle is close to the conch margin, has thick connecting rings which are tubular at the dorsal side (the side directed toward the conch center) and concave at the ventral side (Fig. 6D). The septal necks are short, thickened and orthochoanitic to suborthochoanitic (Figs 8C, 50A).
RemarksThe curvature of the conch of this species is relatively weak compared with the other cyrtocones from the Olenidsletta Member (e.g., Lawrenceoceras larus sp. nov., Valhalloceras floweri). The species can be distinguished from the superficially similar Valhalloceras floweri by its weaker curvature and relatively low angle of expansion. The septal necks are very similar to the necks of Middle Ordovician species of Richardsonoceroides and Richardsonoceras (see Kröger et al. 2009b: fig. 9.10–11). The new genus differs from Richardsonoceroides in having a depressed conch cross section and siphuncular segments with a concave ventral and tubular dorsal shape. Olenidslettoceras farmi gen. et sp. nov. is provisionally placed within the Phtanoncoceratidae because of its combination of characteristic septal necks, the presence of a partly tubular siphuncle and exogastric conch curvature.
Notes
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Linked records
Additional details
Biodiversity
- Collection code
- FMNH-P
- Family
- Rioceratidae
- Genus
- Olenidslettoceras
- Kingdom
- Animalia
- Material sample ID
- FMNH-P30345 , FMNH-P30380
- Order
- Tetrabranchia
- Phylum
- Mollusca
- Scientific name authorship
- Kröger & Pohle
- Species
- farmi
- Taxonomic status
- gen. et sp. nov.
- Taxon rank
- species
- Type status
- holotype , paratype
- Taxonomic concept label
- Olenidslettoceras farmi Kröger & Pohle, 2021
References
- Kroger B., Zhang Y. & Isakar M. 2009 b. Discosorids and oncocerids (Cephalopoda) of the Middle Ordovician Kunda and Aseri Regional Stages of Baltoscandia and the early evolution of these groups. Geobios 42: 273 - 293. https: // doi. org / 10.1016 / j. geobios. 2008.09.006