Trocholites freyjae, Aubrechtová & Korn, 2025

Trocholites freyjae sp. nov.

urn:lsid:zoobank.org:act:7EC4E3F9-662D-4F88-BC4F-81779A9EB017

Fig. 18 View Fig ; Table 9 View Table 9

Trocholites incongruus – Angelin 1880: 11, pl. 9 fig. 17.

Diagnosis

Species of the genus Trocholites with an adult conch diameter of 30–40 mm. Conch in the last whorl thickly discoidal (CWI = 0.45–0.50) and evolute (UWI ~ 0.46). Whorl profile moderately depressed (WWI = 1.60–1.80) with trumpet-shaped aperture (ventral and lateral flares). Whorl width slightly increasing, whorl height slightly decreasing in last quarter volution. Phragmocone chambers moderately long to long (RCL = 0.20–0.40). Suture line straight or with shallow ventral lobe. Siphuncle subdorsal in position with relative diameter of ~ 0.20.

Etymology

After Freyja, the Norse goddess of love, beauty, fertility and war.

Type material

Holotype

GERMANY • probably Brandenburg ; Neben and Krueger Coll.; illustrated in Fig. 18A View Fig ; MB.C. 32171 .

Paratypes

ESTONIA • 1 spec.; Osmussaar ; Lasnamägi Regional Stage ; illustrated in Fig. 18C View Fig ; TUG 46-167 .

GERMANY – Brandenburg • 1 spec.; Niederfinow ; Lasnamägi Regional Stage ; Neben and Krueger Coll.; illustrated in Fig. 18B View Fig ; MB.C. 32172 .

SWEDEN • 1 spec.; Altsarbyn (earlier spelling Alsarbyn, Dalarna); Darriwilian Stage; Angelin Coll.; figured by Angelin (1880: pl. 9 fig. 17), re-illustrated here in Fig. 18D View Fig ; NRM Mo 152355 .

Description

Holotype MB.C.32171 ( Fig. 18A View Fig ) is a specimen in the terminal growth stage with 31 mm conch diameter. With a diameter of 31 mm, the conch is discoidal (CWI = 0.48) and evolute (UWI = 0.46). The whorl profile is moderately depressed (WWI = 1.85) and impressed dorsally; it possesses broadly rounded flanks and venter. The body chamber is almost complete at about 220 degrees in length. In the last quarter, it slightly decreases in height from 8.4 mm to 8.0 mm. The aperture possesses conspicuous lateral and ventral flares, which give the aperture a trumpet-like appearance. Since the body chamber is exfoliated, the shell ornament is visible only on the chambered part of the conch, where it consists of rather sharp, densely spaced rursiradiate lirae; the internal mould of the body chamber shows faint impressions of raised lirae or narrow annuli.

Paratype MB.C.32172 ( Fig. 18B View Fig ) is a conch with 34 mm diameter and consists of 3.25 volutions; more than the last half whorl belongs to the incomplete body chamber. In the last half volution, the conch is thinly discoidal (CWI = 0.43) and evolute (UWI = 0.49). The whorl height decreases from 8.8 mm at the beginning of the body chamber to 8.2 mm in its apertural end; the whorl width of the body chamber increases slightly in this interval from 13.8 mm to 14.3 mm. The whorl profile becomes increasingly depressed in the last half a whorl (WWI changes from 1.58 to 1.74); it has rounded flanks and a very slightly flattened venter. The shell is ornamented with irregularly spaced, rursiradiate lirae, which are occasionally approximated and raised. The phragmocone chambers are moderately long (RCL ranges between 0.20 and 0.35) in the last half of the phragmocone.

Paratype TUG 46-167 ( Fig. 18C View Fig ) is a preadult specimen with 28 mm conch diameter; one third of the last volution is occupied by the body chamber. At its maximum diameter, the conch is discoidal (CWI = 0.44) and widely umbilicate (UWI = 0.52). The whorl profile shows broadly rounded flanks and a slightly flattened venter; it is moderately depressed (WWI = 1.80). Both the whorl width and whorl height increase gradually, but it appears that the whorl height in the last quarter whorl starts to decrease slightly. The phragmocone chambers are moderately long (RCL = 0.30–0.40) in the last whorl; the suture line is almost straight with a very shallow external lobe.

Paratype NRM Mo 152355 ( Fig. 18D View Fig ) is a preadult conch with 26 mm diameter with two whorls preserved; the body chamber is not present. At the maximum diameter, the conch is thickly discoidal (CWI = 0.50); the latest whorl profile is moderately impressed (IZR = 0.23) and moderately depressed (WWI = 1.76) with rounded flanks and venter. The coiling rate is low (WER = 1.65). The ornament is preserved only in small shell relicts; it consists of sharp, regularly spaced lirae and does not leave any traces on the internal mould. The phragmocone chambers are moderately long (RCL = 0.25 in the external volution); the latest two chambers appear to be shortened. The suture line is almost straight with a very shallow and wide external lobe. At the maximum diameter, the siphuncle has a subdorsal position (RSP = 0.86) and a relative diameter (RSH) of about 0.20.

Remarks

Trocholites freyjae sp. nov. differs from T. macrostoma , T. contractus , T. baldri sp. nov., T. glacialis sp. nov., T. sp. 1 and T. sp. 3 in the combination of whorl width increase and whorl height decrease in the terminal body chamber.

In Trocholites depressus , the whorl height may slightly decrease in last quarter volution, as in T. freyjae sp. nov. However, T. depressus differs in that the last whorl is more discoidal (CWI up to 0.40 vs up to 0.50), the whorl profile tends to be less depressed (WWI = 1.25–1.60 vs 1.60–1.80) and the siphuncle is marginodorsal (vs subdorsal) in position and relatively wider in diameter (RSH ~ 0.30 vs 0.20 in the last whorl).

Paratype NRM Mo 152355 was previously figured by Angelin (1880) and used by Schröder (1891) as a syntype of Trocholites remelei . The type collection of that species consisting of three specimens (NRM Mo 152355, NRM Mo 152354, MB.C.11562) is revised herein and all three were found to represent different species.

Paratype NRM Mo 152355 differs from MB.C.11562 (lectotype of T. remelei ) by being more discoidal (CWI = 0.50 at dm 26 mm vs 0.59 at dm 22 mm) with less rapidly expanding whorls (WER = 1.65 at dm 26 mm vs 1.87 at dm 22 mm); its whorl profile is more depressed (WWI = 1.76 at dm 26 mm vs 1.43 at dm 22 mm) and less impressed (IZR = 0.23 at dm 26 mm vs 0.34 at dm 22 mm).

Paratype NRM Mo 152355 is additionally distinguished from NRM Mo 152354 (holotype of Trocholites tureki sp. nov.) because it is stouter (CWI = 0.50 at dm 26 mm vs 0.41 at dm 22 mm) with more strongly depressed whorls (WWI = 1.76 at dm 26 mm vs 1.46 at dm 22 mm). Most remarkably, the shell surface of NRM Mo 152355 is ornamented only by sharp lirae and lacks any annuli or ribs, unlike in the representatives of T. remelei and T. tureki .