Paprothites dorsoplanus (Schmidt, 1924)

Figs 10F, 103–105; Tables 100–101

Pseudarietites westfalicus var. dorsoplana Schmidt, 1924: 152, pl. 8 fig. 13.

Pseudarietites dorsoplanus dorsoplanus – Vöhringer 1960: 161, pl. 6 fig. 10, text-fig. 39. — Korejwo 1979: pl. 12 fig. 2.

Paprothites dorsoplanus – Korn 1994: 75, text-figs 70a–b, 71c, 72a; 2006: text-fig. 4e. — Korn & Weyer 2003: 100, pl. 2 figs 22–23. — Sprey 2002: 53, text-fig. 18h. — Kullmann 2009: text-fig. 5.4.

non Paprothites dorsoplanus – Dzik 1997: 109, text-fig. 29c.

Diagnosis

Species of Paprothites with a conch reaching 30 mm diameter. Conch at 15 mm dm thinly discoidal, subevolute (ww/dm ~0.40; uw/dm ~0.40). Whorl profile at 15 mm dm weakly depressed (ww/wh ~1.30); coiling rate moderate (WER ~1.80). Venter rounded, umbilical margin rounded. On the flank 25 sharp ribs with weakly concave course.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen, railway cutting; Hangenberg Limestone; Schmidt Coll.; illustrated by Schmidt (1924: pl. 8, fig. 13) and Korn (2006: text-fig. 4e); re-illustrated here in Fig. 103A; BGRB X5715.

Additional material

GERMANY • 3 specimens; Rhenish Mountains, Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d; Vöhringer Coll.; GPIT-PV-63967, GPIT-PV-63969, GPIT-PV-63971 • 38 specimens; Rhenish Mountains, Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d 1; Weyer 1993– 1994 Coll.; MB.C.31199.1–38 • 5 specimens; Rhenish Mountains, Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d1a; Weyer 1993–1994 Coll.; MB.C.31200.1–5 • 11 specimens; Rhenish Mountains, Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d1b; Weyer 1993–1994 Coll.; MB.C.31201.1–11 • 12 specimens; Rhenish Mountains, Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d2; Weyer 1993–1994 Coll.; MB.C.31202.1–12 • 1 specimen; Rhenish Mountains, Oberrödinghausen, road cutting; Hangenberg Limestone; Korn 1977 Coll.; MB.C.31203 • 1 specimen; Rhenish Mountains, Oberrödinghausen, road cutting; Hangenberg Limestone, bed 3d; Korn & Weyer 2000 Coll.; MB.C.31204 • 1 specimen; Rhenish Mountains, Hasselbachtal; Hangenberg Limestone, bed 51; Weyer 1993–1994 Coll.; MB.C.5237.3 • 4 specimens; Rhenish Mountains, Hasselbachtal; Hangenberg Limestone, bed 53; Weyer 1993–1994 Coll.; MB.C.5238.3–6 • 1 specimen; Rhenish Mountains, Hasselbachtal; Hangenberg Limestone, bed 57; Weyer 1993–1994 Coll.; MB.C.5240.9 • 1 specimen; Rhenish Mountains, Oese, old quarry; Hangenberg Limestone, bed 25; Weyer & Korn 2000 Coll.; MB.C.5261.1 • 3 specimens; Rhenish Mountains, Oese, old quarry; Hangenberg Limestone, bed 22; Weyer & Korn 2000 Coll.; MB.C.5262.1, MB.C.5262.6–MB.C.5262.7.

Description

Holotype BGRB X5715 is a well-preserved specimen with 13 mm conch diameter (Fig. 103A). It is representative for the morphology of the species, in which morphological variation ranges only within narrow limits. The specimen is thinly discoidal and subevolute (ww/dm = 0.44; uw/dm = 0.39) with a weakly depressed crescent-shaped whorl profile (ww/wh = 1.30) and a moderately high aperture (WER = 1.75). Its sculpture shows 24 protracted ribs on one volution; these are coarsest on the inner flank and fade out in the ventrolateral area. The interspaces between the ribs are occasionally deepened to constrictions, which wedge out on the outer flank near the venter.

A series of four well-preserved specimens (Fig. 104) between 9 and 22.5 mm conch diameter are suitable to complement the species description. They show slight variation in the strength and number of the ribs; while the smaller specimens MB.C.31201.4 (9 mm dm; Fig. 104D) and MB.C.31201.3 (10 mm dm; Fig. 104C) have rather weak ribs, these are coarser, particularly on the umbilical margin, in specimen MB.C.31201.2 (16 mm dm; Fig. 104B) and also in the largest available specimen MB.C.31201.1 (22.5 mm dm; Fig. 104A). In the latter specimen, the ribs extend with linear course and radial direction across the inner and middle flank; they turn forward on the outer flank where the fade out. Specimens MB.C.31201.3 and MB.C.31201.2 show incipient ventrolateral furrows. For the demonstration of the low variation in conch geometry and sculpture, another eight specimens are shown (Fig. 104E–L).

Paprothites dorsoplanus has a rather simple conch ontogeny, which can be described using the cross section of specimen GPIT-PV-63971 with 8 mm conch diameter (Fig. 105A) and some other specimens (Fig. 105C–E). The ww/dm trajectory is monophasic with a continuous decrease from 0.90 at 1 mm dm to 0.45 at 20 mm dm. The uw/dm trajectory is weakly triphasic and oscillating between 0.30 and 0.45 and the WER is stable at a value around 1.70 between 1.5 and 20 mm diameter. Throughout ontogeny, the whorl profile is crescent-shaped and depressed with an ontogenetic trend to a more strongly compressed shape.

Remarks

Paprothites dorsoplanus is easily distinguishable from the co-occurring P. raricostatus and P. beckeri sp. nov. by the much coarser ribs. On the other side, P. ruzhencevi and P. kullmanni sp. nov. have coarser and sharper ribs than P. dorsoplanus . Furthermore, the ribs are much more strongly bent forward across the flanks in P. ruzhencevi .