Trocholites tureki, Aubrechtová & Korn, 2025

Trocholites tureki sp. nov.

urn:lsid:zoobank.org:act:789D9C9E-67E0-45E5-9F31-3FCE54C8FB0F

Fig. 24 View Fig ; Table 15 View Table 15

Trocholites incongruus – Angelin 1880: 11, pl. 9 figs 15–16, 18.

Diagnosis

Species of the genus Trocholites with conch in adult growth stage discoidal (CWI ~ 0.40) and evolute (UWI ~ 0.48). Whorl profile weakly depressed (WWI ~ 1.46) and weakly impressed (IZR ~ 0.17), rounded from lateral and ventral side. Coiling rate is low (WER ~ 1.71). Shell ornament with low annuli and / or widely spaced, and lirae.

Etymology

After Vojtěch Turek (Prague, Czech Republic) in the honour of his contribution to the knowledge on Palaeozoic cephalopods.

Type material

Holotype

SWEDEN • Altsarbyn (earlier spelling Alsarbyn), Dalarna; Darriwilian Stage; Wegelin Coll.; illustrated by Angelin (1880: pl. 9 figs 15–16, 18), re-illustrated here in Fig. 24A View Fig ; NRM Mo 152354 .

Paratype

ESTONIA • 1 spec.; Osmussaar 1 ; Uhaku Regional Stage ; Toom Coll.; illustrated in Fig. 24B View Fig ; GIT 362 - 721-2 .

Description

Holotype NRM Mo 152354 ( Fig. 24A View Fig ) is a subadult or adult conch with 22 mm diameter with nearly three whorls preserved. The last 45 degrees of the conch belong to the body chamber, which is incomplete. In the last 270 degrees, the conch becomes increasingly discoidal (CWI = 0.49–0.41) and increasingly umbilicate (UWI = 0.41–0.48). The whorl profile is rounded from ventral and lateral sides and weakly depressed; the WWI decreases from 1.50 (dm = 14.6 mm) to 1.25 (dm = 19.4 mm) and then again increases to 1.46 at the body chamber (dm = 22 mm). The coiling rate at the maximum diameter is low (WER = 1.71). The shell ornament consists of closely spaced, thin to raised lirae and low ribs, which are not reflected on the internal mould of the conch; the ribs are present from earliest preserved volution up to the external volution, where they form a rather deep ventral sinus. In the internal volutions, node-like elements are present laterally. The phragmocone chamber length (RCL) is 0.29 in the external volution; suture lines are almost straight with a shallow external lobe.

Paratype GIT 362-721-2 ( Fig. 24B View Fig ) is a nearly complete conch with 28 mm diameter and consists of four whorls; the last half a whorl belongs to the incomplete body chamber. At the maximum diameter, the conch is discoidal (CWI = 0.40) and evolute (UWI = 0.46). The whorl profile is ventrally and laterally rounded and weakly depressed; the WWI decreases from 1.50 to 1.29 (dm = 24 mm) and then increases to 1.40 (dm = 28 mm). The shell ornament consists from 1) widely spaced ribs which are in the last half a whorl replaced by 2) narrowly spaced ribs or accumulations of lirae (less prominent ventrally than laterally), and 3) fine lirae. Only the riblets are reflected on the internal mould of the conch. The phragmocone chamber length (RCL) is ~ 0.25 in the external volution and the last chamber is shortened; suture lines are almost straight.

Remarks

Holotype NRM Mo 152354, previously illustrated by Angelin (1880), was used by Schröder (1891) as one of three syntypes of Trocholites remelei . All three specimens (NRM Mo 152355, NRM Mo 152354, MB.C.11562) are assigned here to different species on the basis of substantial differences in conch geometry and shell ornament. Holotype NRM Mo 152354 specifically differs from lectotype MB.C.11562 of Trocholites remelei by being more discoidal (CWI = 0.41 vs 0.59 at dm ~ 22 mm), more evolute (UWI = 0.71 vs 0.87 at dm ~ 22 mm), less rapidly expanding (WER = 1.71 vs 1.87 at dm ~ 22 mm) and its whorls are less impressed (IZR = 0.17 vs 0.34 at dm ~ 22 mm); the ornament in NRM Mo 152354 is not visible on internal mould. The holotype NRM Mo 152354 also differs from paratype NRM Mo 152355 of Trocholites freyjae sp. nov. because it is narrower (CWI = 0.41 at dm 22 mm vs 0.50 at dm 26 mm) with less depressed whorls (WWI = 1.46 at dm 22 mm vs 1.76 at dm 26 mm); in addition, the shell surface is annulated in NRM Mo 152355 (but with sharp lirae in NRM Mo 152354).

The holotype is unique in the collection by the presence of distinct lirae and annuli covering the entire shell surface and is therefore placed in a separate species.Another specimen, GIT 362-721-2, is assigned to the new species because it corresponds to the holotype in shell geometry. The only difference between the two is the presence of widely spaced ribs on the inner whorls of GIT 362-721-2. Most similar to both specimens is the specimen MB.C.32182 of T. sp. 4 and some representatives of T. depressus ( Fig. 7 View Fig ), which also have annuli or ribs on the shell surface. In the latter two species, however, the shell ornament is much finer and / or irregular in spacing and thickness. In addition, the specimens of Trocholites depressus generally have lower coiling rate (WER ~ 1.65 vs 1.71) in the adult growth stage.