Strandoceras sulevipoegi sp. nov. urn:lsid:zoobank.org:act: 8846BE74-EF9D-437F-B22A-493CB44C1E89 Figs 31E, 41B, D, 42A, 43A Diagnosis Strandoceras with relatively slender conch; angle of expansion up to 34°; mature body chamber nearly tubular, slightly endogastrically curved, ca 60–65 mm high and 75 mm long, with an oval compressed conch cross section (CHI ca 1.3) with a narrower prosiphuncular conch margin; ornamented with fine transverse lirae. Etymology From Sulevipoeg, a hero in the Estonian national epic, Friedrich R. Kreutzwald’s (1803–1882) poem “Kalevipoeg”, a friend of Kalevipoeg. See Strandoceras kalevipoegi sp. nov. Type material Holotype ESTONIA • Salu; Pirgu Regional Stage; TUG 1745-209. Paratypes ESTONIA • 1 spec.; same data as for holotype; TUG 1745-209 • 1 spec.; Förby shore; Pirgu Regional Stage; TUG 1745-176 • 1 spec.; Niibi quarry; Moe Formation, Pirgu Regional Stage; TUG 42-433 • 1 spec.; Paluküla quarry; Kõrgessaare Formation, Vormsi Regional Stage; GIT 426-565 • 1 spec.; Salutaguse; Moe Formation, Pirgu Regional Stage; TUG 1745-292 • 1 spec.; Saxby old quarry; Moe Formation, Pirgu Regional Stage; TUG 1745-198 • 1 spec.; Saxby shore; Kõrgessaare Formation, Vormsi Regional Stage; TUG 899-55 • 1 spec.; Sutlepa quarry; Adila Formation, Pirgu Regional Stage; TAM G149:26 • 1 spec.; Tapa; Moe Formation, Pirgu Regional Stage; GIT 426-48 • 1 spec.; same data as for preceding; TUG 1239-6 • 1 spec.; Vormsi Island; Vormsi–Pirgu regional stages; TUG 42-399. Description Only relatively incomplete fragments are known from this species. They differ from other species of this genus in being more slender. The most complete outline of the relatively weak conch curvature is preserved in specimen TUG 42-399 (Fig. 41D), which is a fragment of the mature body chamber and eight chambers of the phragmocone, but in which the internal characters and the conch width are not preserved. The mature body chamber is preserved in six specimens with conch heights of 62–64 mm (TUG 42-399, TUG 899-55, TUG 1745-176, GIT 426-565, and widths of 48 mm (TUG 899-55, TUG 1239-6) at their bases (CHI = 1.3). The conch cross section is oval with a narrower prosiphuncular conch margin. The total length of the mature body chamber is 75 mm (TUG 42-399, TUG 899-55, TUG 1745- 176) (see Fig. 43A). The mature body chamber is slightly endogastrically curved and in lateral view has a convex margin at the antisiphuncular side and a concave margin on the prosiphuncular side. The conch height at the mature aperture is ca 65 mm (specimen TUG 1745-176). The holotype is a fragment of a phragmocone with a length of ca 140 mm, preserving its relatively weak curvature and low angle of expansion which is 22° between conch heights of 28 mm and 33 mm, and 32° between conch heights of 33 mm and 44 mm (Fig. 41B). The outer shell is preserved in the holotype. It is ornamented with fine transverse lirae or growth bands, similar to those present in S. sphynx, but coarser (Fig. 32E). The sutures form shallow lateral lobes, and are 8 mm apart where the conch height is 35 mm (RCL = 0.23). The siphuncle is marginally positioned at the concave side of the conch curvature (endogastric curvature) with widely expanded segments. The width of the septal foramen is ca 6 mm, the width of the siphuncular segment 14 mm, and the chamber length 8 mm where the conch height is ca 50 mm (RSH = 0.12, RSS = 2.3, SCR = 1.75). Specimen TUG 42-433 is a relatively complete fragment of a phragmocone without outer shell preserved which permits measurement of the trajectory of the angle of expansion (Fig. 42A); it expands with a minimum angle of 3° between conch heights of 60 mm and 61 mm and a maximum angle of 31° between conch heights of 37 mm and 48 mm. Comparison This is a relatively slender Strandoceras. The conch height at the base of the mature body chamber is 60–65 mm, which is considerably smaller than in S. kalevipoegi sp. nov. with a conch height of ca 75 mm, and in S. sphynx, which measures ca 70 mm at the base of the body chamber. Strandoceras tyriense is smaller (conch height at base of mature body chamber is ca 55 mm) and its phragmocone is more strongly curved.

Published as part of Kröger, Björn, 2025, The Lyckholm acme of cephalopods - Review of the late Katian (Vormsi-Pirgu regional stages) Ordovician cephalopods of Estonia, pp. 1-169 in European Journal of Taxonomy 978 on pages 123-124, DOI: 10.5852/ejt.2025.978.2801, http://zenodo.org/record/14988376