Rhynchorthoceras sp.

Aubrechtová, Martina & Korn, Dieter, 2022, Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician), European Journal of Taxonomy 799 (1), pp. 1-108 : 27

Rhynchorthoceras sp.

Material examined

GERMANY • 1 spec.; Brandenburg, Eberswalde; Ordovician, Upper Grey Orthoceratite Limestone; MB.C.30510 • 1spec.; Brandenburg, Gransee (Ruppin); Ordovician, Upper Grey Orthoceratite Limestone; Kirchner Coll.; MB.C.11689 • 2 specs; Brandenburg, Hohensaaten; Ordovician, Upper Grey Orthoceratite Limestone; Neben and Krueger Coll.; MB.C.30511 , MB.C.30512 • 2 specs; Brandenburg, Niederfinow; Ordovician, Upper Grey Orthoceratite Limestone; MB.C.30513 , MB.C.30514 • 1 spec.; Mecklenburg- Vorpommern, Dwasieden ( Island of Rügen ); Ordovician, Upper Grey Orthoceratite Limestone; MfN excursion 1964 Coll.; MB.C.11711 • 1 spec.; Mecklenburg-Vorpommern, Lebbin; Ordovician ; Böhm 1906 Coll.; MB.C.11713 • 2 specs; Mark?; Ordovician ; MB.C.11705.1 , MB.C.11705.2 .

POLAND • 1 spec.; Silesia, Kunzendorf; Ordovician; MB.C.11712 • 1 spec.; West Pomerania, Island of Chrząszczewska (former Gristow); Ordovician; MB.C.11710 .

SWEDEN • 1 spec.; Island of Öland , Gärdslösa; Ordovician; Bottke Coll.; MB.C.29652 .

Remarks

In the collection under study, there are several specimens of orthoconic or weakly cyrtoconic lituitids, which have expansion angles between 10–14° ( Fig. 13A , Table 2 ), a circular whorl profile and a centrally located siphuncle with SDR between 0.12 and 0.14 ( Fig. 13B , Table 3 ). Thus, the specimens are assigned here to the genus Rhynchorthoceras . Since the shell surface in the above specimens is covered by conspicuously sinuous and asymmetric lirae, which form deep sinuses on the flanks and the venter, they should be assigned either to R. breynii from the Middle Ordovician erratics of northern Germany, or the other European species of Rhynchorthoceras with sinuous lirae, i.e., R. beyrichii (from late Darriwilian erratics of Poland), R. helgoeyense Sweet, 1958 (from the late Middle or early Late Ordovician of Norway) and R. zaddachi (from the Darriwilian erratics of the Kaliningrad Region, Russia). Unfortunately, these species are rare and unequivocally known only from the type material, which has not been revised since the species descriptions and was not available for study herein. In addition, the ornament in the specimens in discussion is often incompletely or poorly preserved. Any species-level assignment of these specimens is thus avoided herein.

Figures

Fig. 13. Conch expansion rates (A) and siphuncle diameter rates (B) in species of Rhynchorthoceras Remelé, 1882.