Archigeisonoceras picus, Kröger, 2004

Kröger, Björn, 2004, Revision of Middle Ordovician orthoceratacean nautiloids from Baltoscandia, Acta Palaeontologica Polonica 49 (1), pp. 57-74 : 67-68

publication ID

https://doi.org/ 10.5281/zenodo.13272378

persistent identifier

https://treatment.plazi.org/id/03F28786-B179-FF9B-FCAE-F88F6C4FDAFE

treatment provided by

Felipe

scientific name

Archigeisonoceras picus
status

sp. nov.

Archigeisonoceras picus sp. nov.

Figs. 10A View Fig , 12B, E View Fig , 13I.

Holotype: The adult specimen NRM−Mo 14455a–c, which has juvenile as well as adult chambers and parts of the living chamber. The recrystallized external shell is partly preserved.

Type locality: Resmo of Öland ( Sweden).

Type horizon: Limbata Limestone (Volkhovian).

Derivation of the name: From Latin picus , woodpecker or bird of prey, referring to the shape of the shell.

Material.— One specimen available in the NRM (termed O. picus nomen nudum by Holm) .

Diagnosis.— Archigeisonoceras relative cyrtocone, of medium size (maximum diameter: 38 mm) and with high apical angle.

Description.—Conch form: Slightly cyrtoconic in cross section, slightly compressed. Apical angle of the conch 6.3°.

Ornamentation: External shell smooth with minute, irregular, spaced growthlines.

Phragmocone: Chamber height 0.2of the respective diam − eter. Sutures straight. Septa simple concave. Short orthochoanitic septal necks in adult parts of the phragmocone, suborthochoanitic in apicad parts. Siphuncle subcentral to central. Siphuncular diameter 0.1 of the respective diameter of the conch. In middle parts of the phragmocone episeptal deposits ( Fig. 12E View Fig ) and well developed endosiphuncular annuli and asymmetric lining in the apical parts of the siphuncle ( Fig. 12B View Fig ).

Living chamber: Adult living chamber cylindrical. Aperture not known.

Comparison.— Archigeisonoceras picus differs from Archigeisonoceras repplingense in its greater adult size, and the lower height of chamber, from Archigeisonoceras folkeslundense in its lower chamber height and smaller adult size and from Archigeisonoceras elegatum in its narrower siphuncle.

Distribution.— Archigeisonoceras picus occurs only in the Limbata Limestone (Volkhov) of Öland.

NRM

Swedish Museum of Natural History - Zoological Collections

Darwin Core Archive (for parent article) View in SIBiLS Plain XML RDF