Trocholites vodickai, Aubrechtová & Korn, 2025

Trocholites vodickai sp. nov.

urn:lsid:zoobank.org:act:6CA0C13A-9BDC-41B9-8E08-AFE05FB363C5

Fig. 25 View Fig ; Table 16 View Table 16

Diagnosis

Species of the genus Trocholites with an adult conch diameter of about 40 mm. Conch in the last whorl thinly discoidal (CWI ~ 0.40) and evolute (UWI ~ 0.46). Whorl profile weakly depressed (WWI = 1.25–1.50) with rounded flanks and slightly flattened venter in the adult stage. Shell ornament with fine, rursiradiate lirae; internal mould of body chamber with faint annular impressions. Phragmocone chambers moderately long (RCL = 0.30–0.40). Suture line straight.

Etymology

After Jakub Vodička (Prague, Czech Republic), for his contribution to the chitinozoan research in Bohemia.

Type material

Holotype

POLAND – West Pomerania • Ustronie Morskie; Lasnamägi or Uhaku regional stages ; Müldner Coll.; illustrated in Fig. 25A View Fig ; MB.C. 32177

Paratype

GERMANY – Brandenburg • 1 spec.; Hindenberg near Calau ; Ordovician; Krueger Coll.; illustrated in Fig. 25B View Fig ; MB.C. 32178 .

Description

Holotype MB.C.32177 ( Fig. 25A View Fig ) is an adult conch with 41 mm diameter, of which the last ~ 220 degrees of the external volution belongs to the body chamber. In the last quarter volution, the conch becomes more discoidal (CWI decreases from 0.46 to 0.40) and slightly more evolute (UWI changes from 0.44 to 0.46); the whorl profile shows broadly rounded flanks and venter. It is decreasingly depressed; during the last quarter of a volution, the WWI decreases from 1.37 to 1.27. The body chamber shows a terminal aperture with flares and a ventral sinus. The ornament consists of fine, rursiradiate lirae; faint annular impressions are present on the internal mould of the terminal body chamber. The phragmocone chambers are moderately long (RCL = 0.33).

Paratype MB.C.32178 ( Fig. 25B View Fig ) is a conch in the adult growth stage; it is distorted at one side and has a diameter of 39 mm. More than half of the last volution belongs to the body chamber. In the last quarter whorl, the conch is discoidal (CWI changes slightly from 0.46 to 0.44) and increasingly evolute (UWI changes from 0.37 to 0.45). The whorl profile is weakly depressed (WWI increases from 1.43 to 1.50) and shows broadly rounded flanks and a slightly flattened venter. At the maximum conch diameter, the whorl height appears to decrease slightly (from 11.9 mm to 11.5 mm) from about the mid-length of the terminal body chamber. The body chamber begins to produce flares at its terminal aperture. The shell is ornamented by fine, rursiradiate lirae; the internal mould of the body chamber has shallow annular impressions. The phragmocone chambers are rather long (RCL = 0.38).

Remarks

Trocholites vodickai sp. nov. is rather similar to T. macrostoma but the latter has a more strongly depressed adult body chamber (WWI ~ 1.70 vs 1.25–1.50 in T. vodickai ) and a wider umbilicus (UWI ~ 0.55 vs ~ 0.45).

Trocholites vodickai sp. nov. shows some similarity to T. vortex sp. nov., but the former are smaller in adult size (40 in contrast to more than 50 mm), the last whorl is more discoidal (CWI ~ 0.40 vs 0.47) with shorter phragmocone chambers in the last volution (RCL = 0.30–40 vs 0.47).

Trocholites luna sp. nov. differs from T. vodickai sp. nov. in the greater adult size (50 mm vs 40 mm); the last whorl is more evolute (UWI ~ 0.52 vs 0.46) and the shell ornament in inner whorls has raised lirae or accumulation of lirae instead of fine, rursiradiate lirae.

The two specimens of T. kadakaensis sp. nov. differ from those of T. vodickai sp. nov. because their last whorl is less discoidal (CWI ~ 0.48 vs 0.40) and the whorl profile is much more depressed (WWI ~ 1.80 vs 1.25–1.50) with a distinct decrease in width and height towards the terminal aperture.

In the holotype of T. zaryensis sp. nov., the last whorl is also less discoidal (CWI ~ 0.57 vs 0.40) and slightly more narrowly evolute (UWI ~ 0.42 vs 0.46); the whorl profile is more depressed (WWI ~ 1.82 vs 1.25–1.50).

Trocholites depressus is generally rather similar in conch geometry to T. vodickai sp. nov. but the specimens of the former tend to have a more depressed whorl profile (WWI up to 1.60) in the last volution and the ornament on inner whorls has ribs.

Geographic and stratigraphic occurrence

Northern Poland and northern Germany; late Darriwilian, Middle Ordovician.