Spyroceras damesi (Krause 1877), Pridoli, Beyrichienkalk glacial erratic boulders, a: Almost complete specimen MB C.865.3, Voigtsdorf. b: Lectotype MB C.862, Bydgoszcz. c: Thin section of phragmocone MB C.865.2, Voigtsdorf. d: MB C.864.1 Oderberg. e: Fragmentary specimen ZPAL N/873 in the Beyrichienkalk rock matrix, Międzyzdroje. a-b, e: x 1.5; c: x 3; d: x 4

Spyroceras damesi (Krause, 1877), Pridoli, Beyrichienkalk, Orłowo  a: Reconstruction of living chamber based on specimen ZPAL N/751; approximately natural size. b: Longitudinal section through siphuncle, ZPAL N/753. c: Reconstruction of a phragmocone section based on ZPAL N/742.

Diagnoza

E m e n d e d  d i a g n o s i s : Conchs at early stages weakly annulated and ornamented with sparse longitudinal riblets, later smooth. Cameral deposits with equally developed mural and episeptal parts; siphuncular deposits tend to unify in continuous ventral lining.

D i a g n o s t i c  d i f f e r e n c e s : S. damesi is distinct from all known species of Spyroceras in that the longitudinal ribs do not continue to the adult stages but gradually disappear. At least in better known Ordovician species of Gorbyoceras and Spyroceras cameral deposits developed only murally. It has to be kept in mind that both siphuncular and cameral deposits in orthoconic nautiloids show extremely wide ranges of intrapopulation variability (MUTVEI: 1964; DZIK 1984), though they are generally believed to be diagnostic at generic or even family level. Kionoceratid genera other than Spyroceras, such as Gorbyoceras SHIMIZU & OBATA 1936 and Kionoceras HYATT 1884, differ in the much greater rate of conch diameter expansion. 

Porównanie

Autekologia

Występowanie geograficzne

The species is known only from the Beyrichienkalk erratic boulders, widely
occurring in north-eastern Germany and Poland. 

Zasięg czasowy

Materiały muzealne

Literatura

Dzik J.,  Kiselew G.N. 1995. The Baltic nautiloids Cyrtoceras ellipticum LOSSEN 1860, C. priscum Eichwald 1861, and Orthoceras damesi Krause 1877 Palaont. Z 69: 61-71, Stuttgart.