Strandoceras schmidti ( Teichert, 1930 )

Kröger, Björn, 2025, The Lyckholm acme of cephalopods - Review of the late Katian (Vormsi-Pirgu regional stages) Ordovician cephalopods of Estonia, European Journal of Taxonomy 978, pp. 1-169 : 122-123

Strandoceras schmidti ( Teichert, 1930)

Fig. 42B , 43B

Codoceras schmidti Teichert, 1930: 297 , pl. 8 figs 25–26.

Codoceras schmidti – Strand 1934: 88. ― Miller & Youngquist 1947: 13. ― Balashov 1953a: 207. ― Barskov 1972: 66.

Strandoceras schmidti – Flower in Flower & Teichert, 1957: 57.

Diagnosis

Small, short Strandoceras with angle of expansion of up to ca 35°; conch cross section oval compressed, narrower at ventral side; maximum conch height ca 55 mm; mature body chamber slightly curved and contracted; ornamented with fine transverse lirae.

Material examined

ESTONIA • 1 spec.; Salu; Pirgu Regional Stage ; TUG 1745-25 • 1 spec.; Lääne-Virumaa, Tapa; Moe Formation, Pirgu Regional Stage ; GIT 426-440 .

Type locality and horizon

Kose-Uuemõisa, Harju county, Estonia; Vormsi–Pirgu regional stages (“Lyckholm Stufe” of Teichert 1930).

Description

TUG 1745-25 is a fragment of an endogastrically curved phragmocone and body chamber with parts of the outer shell preserved ( Fig. 43B ). The conch surface is nearly smooth, ornamented only with fine growth lines or growth bands. At the apical end of the specimen, the conch cross section is preserved; it is oval compressed with a narrower margin on the prosiphuncular side, with a conch height and width of 26 mm and ca 24 mm, respectively (CHI = 1.13). The conch height expands with an angle of ca 36° between conch heights of 25 mm and 46 mm. At the base of the body chamber, the conch height is 54 mm. The preserved part of the body chamber is 50 mm long. In lateral view, the antisiphuncular margin is convex throughout the entire length of the conch. The conch margin of the prosiphuncular side is preserved only on the phragmocone and the basal ca 15 mm of the body chamber, it is concave throughout, but straightens adorally. The sutures are straight and directly transverse, 5 mm apart, where the conch height is 34 mm (RCL = 0.15).

The second specimen is less well-preserved, and reliable measurements of angle of expansion and CHI are not possible. The base of the body chamber at this specimen has a height of 43 mm.

Remarks

The type specimen figured in Teichert (1930: pl. 8 figs 25–26), is incompletely preserved, not allowing for a quantification of the angle of expansion, and measurements are not given in Teichert (1930). The diagnosis given herein, therefore, is based on the material described herein combined with the original descriptions in Teichert (1930). A specimen from the Eichwald collection of St Petersburg is described and figured as “ Strandoceras oryx (Eichwald, 1861) ” (sic) in Kiselev (1991), referring to Phragmoceras oryx Eichwald, 1857 . This specimen, collected from an unspecified locality at Hiiumaa, is similar to S. schmidti ( Teichert, 1930) in general shape and size. It is therefore possible that S. schmidti ( Teichert, 1930) is a subjective junior synonym of Phragmoceras oryx Eichwald, 1857 , and that the specimens described herein under S. schmidti should be better placed within Eichwald’s (1857) species. However, because the Eichwald material is currently inaccessible, this problem needs to be solved in a future work.

Figures

Fig. 42.Diagrams of variabilityinconch growth in speciesof Strandoceras Flower, 1946.A. S. kalevipoegi sp. nov. = diamonds; S. sphynx (Schmidt, 1858) = white circles; S. sulevipoegi sp. nov. = black circles. B. S. muhvi sp. nov. = crosses; S. schmidti = stars. Note that distinction of species in conch fragments with conch heights <50 mm is not possible based on angle of expansion. Negative angles indicate decreasing conch heights.

Fig. 43. Fragments of Strandoceras Flower, 1946 of the Vormsi–Pirgu regional stages, Estonia. A. Strandoceras sulevipoegi sp. nov., paratype TUG 899-55, from Saxby shore, Vormsi Island, Vormsi Regional Stage. B. Strandoceras schmidti (Teichert, 1930), specimen TUG 1745-25, from Salu, Pirgu Regional Stage. C. Strandoceras kohilense sp. nov., holotype TUG 47-883, from Kohila quarry, Vormsi Regional Stage. Scale = 20 mm, same scale in all figures, all in lateral view.