Trocholites hospes

Trocholites hospes (Remelé, 1880) Figs 1G–H, 8–12; Table 4 Palaeonautilus hospes Remelé, 1880: 249, pl. 2 fig. 3.? Palaeonautilus hospes Remelé, 1880: 249, pl. 2 fig. 4. Palaeonautilus hospes – Remelé 1881: 2, 13, text-fig.1. — Foerste 1930: 286, pl. 43 fig. 2, pl. 44 figs 4–5. — Balashov 1962: pl. 9 fig. 5. Palaeonautilus (Trocholites) hospes – Remelé 1890: 40, pl. 2 fig. 3. ? Palaeonautilus (Trocholites) hospes – Remelé 1890: pl. 2 fig. 4, pl. 5 fig. 8. ? Trocholites hospes – Schröder 1891: 17 (155), pl. 1(24) figs 8–9. ? Palaeonautilus hospes – Schindewolf 1939: 60, text-fig. 14, pl. 4 fig. 7. Trocholites hospes – Balashov 1953: 244, pl. 5 fig. 3. — Sweet 1958: 96, pl. 8 figs 3, 5. — Neben & Krueger 1971: pl. 32 figs 12–14. Diagnosis Species of the genus Trocholites with an adult conch diameter of 43–60 mm. Conch in the last whorl thickly discoidal (CWI = 0.52–0.60) and subevolute (UWI = 0.30–0.40) with moderately high coiling rate (WER = 1.75–1.90). Whorl profile weakly to moderately depressed (WWI = 1.40–1.80), rounded, venter sometimes slightly flattened, usually moderately embracing (IZR = 0.20–0.30). Whorl width and whorl height stagnant or slightly increasing in last quarter volution. Terminal aperture with ventral and lateral flares. Shell ornament with fine lirae extending with rather deep, rounded ventral sinus. Phragmocone chambers moderately long (RCL = 0.20–0.24). Suture line straight. Material examined BALTIC REGION • 1 spec.; locality unknown; Aseri or Lasnamägi or Uhaku regional stages; Deubel Coll.; illustrated in Fig. 10A; MB.C. 7638. GERMANY – Brandenburg • 1 spec.; Herzsprung (Uckermark); upper Lasnamägi Regional Stage; illustrated by Foerste (1930: pl. 44 fig. 4), re-illustrated here in Fig. 8A; MB.C. 11557 • 1 spec.; Oderberg; Lasnamägi or Uhaku Regional Stage; Neben Coll.; illustrated by Neben & Krueger (1971: pl. 32 fig. 14), re-illustrated here in Fig. 8C; MB.C. 32162 • 1 spec.; Karlstein (Neumark); probably Darriwilian; Neben and Krueger Coll.; illustrated in Fig. 9A; MB.C. 32163 • 1 spec.; Oderberg; upper Lasnamägi Regional Stage; 1936: Neben Coll.; illustrated by Neben & Krueger (1971: pl. 32 figs 12–13), re-illustrated here in Fig. 9B; MB.C. 11556 • 1 spec.; Eberswalde; Lasnamägi or Uhaku Regional Stage; Remelé Coll.; illustrated by Neben & Krueger (1971: pl. 32 figs 1–2), re-illustrated here in Fig. 8D; MB.C. 11555.2 • 1 spec.; Oderberg; upper Lasnamägi Regional Stage; Neben and Krueger Coll.; illustrated in Fig. 9C; MB.C. 32164. POLAND – West Pomerania • 1 spec.; Cieszeniewo; upper Lasnamägi Regional Stage; 1890; Dorow Coll.; illustrated by Foerste (1930: pl. 43 fig. 2, pl. 44 fig. 5), re-illustrated here in Fig. 8B; MB.C. 11558 • 1 spec.; Ustronie Morskie (West Pomerania); Lasnamägi or Uhaku Regional Stage; Müldner Coll.; illustrated in Fig. 9D; MB.C. 32165 • 1 spec.; Ustronie Morskie (West Pomerania); Lasnamägi or Uhaku Regional Stage; Neben and Krueger Coll.; MB.C. 32166. Description Specimen MB.C.11557 (Fig. 8A) is a conch in the terminal stage of growth and has a diameter of about 56 mm. The conch is thickly discoidal (CWI = 0.56) and subevolute (UWI = 0.38). The last whorl is moderately depressed; the WWI decreases from 1.64 to 1.58 during the last quarter volution of the conch. The length of the terminal body chamber is 270 degrees; its venter is slightly flattened. Its aperture possesses ventral and lateral flares producing a deep ventral sinus and prominent ventrolateral lappets. The shell ornament is preserved only in the penultimate whorl and in a very small area at the ventral margin of the aperture; it consists of irregularly spaced, coarse lirae. The internal mould has very low annuli on the venter and in the ventrolateral area. The phragmocone chambers are rather long (RCL = 0.40). The suture line is almost straight and extends with a very broad and shallow external lobe. Specimen MB.C.11558 (Fig. 8B) is an almost complete conch of a fully grown individual with a conch diameter of 51 mm. The conch is thickly discoidal (CWI = 0.58) and subevolute (UWI = 0.37). The whorl profile is moderately depressed; the WWI increases from 1.73 to 1.83 in the last 90 degrees of the volutions. The body chamber has a length of about 220 degrees and possesses ventral and ventrolateral flares; a ventral sinus is developed at the aperture. Small remains of the shell ornament are preserved only in the ventrolateral area near the aperture and in the inner volutions; they consist of fine and irregularly developed lirae. The phragmocone chambers are moderately long (RCL = 0.23). The suture line is almost straight with the exception of a very shallow and broad external lobe. At the beginning of the last whorl, the moderately wide siphuncle has a subdorsal position (RSH = 0.24; RSP = 0.84). Specimen MB.C.32162 (Fig. 8C) is an almost complete adult conch with a conch diameter of 51 mm and has nearly five whorls preserved. The conch is thickly discoidal (CWI = 0.57) and subevolute (UWI = 0.42); the coiling rate is moderate (WER = 1.77). The whorl profile is moderately depressed (WWI = 1.75) and moderately embracing (IZR = 0.24). The specimen is almost completely exfoliated; small remains of the shell ornament are preserved only in the inner whorls, where fine and regularly spaced lirae are present. The phragmocone chambers are moderately long (RCL = 0.22). The suture line is almost straight, but extends with a very shallow and broad external lobe. At about half of the last whorl, the rather thin siphuncle has a subdorsal position (RSH = 0.18; RSP = 0.80). At the base of the body chamber, traces of muscle scar imprints are preserved. Specimen MB.C.32163 (Fig. 9A) is an almost complete, well-preserved adult conch with a diameter of 50 mm. The conch is thickly discoidal (CWI = 0.58) and subevolute (UWI = 0.33) with a moderately high coiling rate (WER = 1.82). The whorl profile is weakly depressed (WWI = 1.50) and strongly impressed dorsally (IZR = 0.33) in the terminal half volution of the conch. The terminal body chamber is slightly longer than half of a volution; its aperture possesses ventral and lateral flares; a ventral sinus is indicated. Remain of the shell are preserved only in small areas; the ornament consists of rather regular, fine lirae. Specimen MB.C.11556 (Fig. 9B) is a well-preserved, almost complete conch, which already represents the final stage of growth with a diameter of 43 mm. In this stage of growth, the conch is thickly discoidal (CWI = 0.56), subevolute (UWI = 0.37) and moderately expanding (WER = 1.83); the whorl profile in the last half volution is rounded, moderately depressed (WWI = 1.59) and moderately impressed dorsally (IZR = 0.27). The length of the terminal body chamber is 250 degrees; its aperture possesses ventral and lateral flares. The shell ornament is preserved only near the aperture and consists of irregularly thick lirae, which turn back already from the umbilical seam and form a rather deep, blunt V-shaped ventral sinus. The phragmocone chambers are moderately long (RCL = 0.24). The suture line extends almost straight across the flank and form a very broad and shallow external lobe. Faint traces of muscle scar imprints are preserved in the rear part of the body chamber. Specimen MB.C.32164 (Fig. 9C) is a well-preserved, subadult individual with 47 mm conch diameter; the conch is thinly discoidal (CWI = 0.52) and subevolute (UWI = 0.35) and the profile of the last whorl is moderately depressed (WWI = 1.53). The whorl profile is crescent-shaped with broadly rounded venter and flanks; an umbilical margin is not discernible. The shell ornament is well-preserved in large areas; it consists of irregularly spaced, fine and slightly thickened lirae. They are directed backwardly right from the umbilical seam and form a deep, blunt V-shaped ventral sinus. Specimen MB.C.32165 (Fig. 9D) is, with a conch diameter of 64 mm, the largest specimen of Trocholites in our collection. The last ~ 0.50 a whorl corresponds to the body chamber. The specimen has a well-preserved shell ornament that consists of fine and almost equally spaced lirae. On the body chamber, the lirae are fine on the flanks, but on the venter they become more prominent and form a rounded, nearly rectangular sinus. Specimen MB.C.7638 (Fig, 10A) is an incomplete conch in the early growth stage with 26.5 mm diameter and was sectioned. During ontogeny (between 4.0 mm and 26.5 mm conch diameter), the conch changes from thickly pachyconic to thinly pachyconic (CWI decreases from 0.82 to 0.71) and from involute to subinvolute (UWI increases from 0.15 to 0.29); the coiling rate decreases markedly (WER drops from 2.60 to 1.67). The whorl profile changes only slightly and remains moderately depressed (WWI = 1.98–1.84), but changes from moderately to strongly impressed (IZR increases from 0.18 to 0.42) (Fig. 10B–D). The shell ornament is not well-discernible; it appears to consist of thin ribs or raised lirae in the internal whorl and only lirae in the outer whorl. The phragmocone chambers are rather long (RCL = 0.39 in the external volution). The siphuncle remains close or in contact with the dorsal shell wall and changes from RSH 0.15 to 0.20 in ontogeny. Remarks Remelé (1880) described and figured two specimens of “ Palaeonautilus hospes ” from late Darriwilian erratics near Heegermühle (Brandenburg, Germany); subsequently these specimens were re-described and re-figured by him (Remelé 1881, 1890). Only one of these two specimens (MB.C.11555.2) is available for study; it was also illustrated by Neben & Krueger (1971: pl. 32 figs 1–2) and is re-illustrated here in Fig. 8D. However, this syntype was assigned to Trocholites remelei by Neben & Krueger (1971). Its internal mould shows some annular ridges in the outermost preserved whorl, but the shell surface is ornamented only with fine lirae, not clusters of raised lirae as in the lectotype of T. remelei (see below). Alternatively, it is possible that the speci