Pseudarietites westfalicus Schmidt, 1924

Pseudarietites westfalicus Schmidt, 1924

Figs 8E View Fig , 110–112 View Fig View Fig View Fig ; Tables 106–107 View Table 106 View Table 107

Pseudarietites westfalicus Schmidt, 1924: 152 , pl. 8 fig. 12.

Pseudarietites westfalicus – Schmidt 1925: 536, pl. 19 fig. 7. — Korn 1994: 78, text-figs 70d–e, 71d, 72b; 2006: text-fig. 4d. — Kullmann 2009: text-fig. 5.2b–c.

Pseudarietites westfalicus westfalicus – Vöhringer 1960: 163, pl. 6 fig. 11, text-fig. 40. — Weyer 1965: 448.

Diagnosis

Species of Pseudarietites with a conch reaching 40 mm diameter. Conch at 15 mm dm thinly discoidal, subevolute (ww/dm ~0.40; uw/dm ~0.42). Whorl profile at 15 mm dm weakly depressed (ww/wh ~1.25); coiling rate low (WER ~1.70). Venter broadly rounded with distinct keel between two distinct grooves, umbilical margin rounded. On the flank 25 sharp ribs with concave course.

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone ; Schmidt Coll.; illustrated by Schmidt (1924: pl. 8, fig. 12) and Korn (2006: text-fig. 4d); re-illustrated here in Fig. 110 View Fig ; BGRB X5716.

Additional material

GERMANY • 3 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone ; Schindewolf 1925 Coll.; MB.C.31212.1–3 • 2 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3b ; Vöhringer Coll.; GPIT- PV-63978, GPIT-PV-63980 • 1 specimen; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3c; Vöhringer Coll.; GPIT-PV-63982 • 1 specimen; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3 a; Korn 1991 Coll.; MB.C.31213 • 22 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3 a; Weyer 1993–1994 Coll.; MB.C.31214.1–22 • 8 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3b ; Weyer 1993–1994 Coll.; MB.C.31215.1–8 • 7 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3c1 ; Weyer 1993–1994 Coll.; MB.C.31216.1–7 • 1 specimen; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3c2 ; Weyer 1993–1994 Coll.; MB.C.31217 • 1 specimen; Rhenish Mountains, Oberrödinghausen , road cutting ; Hangenberg Limestone , bed 3b ; Korn & Weyer 2000 Coll.; MB.C.31218 • 1 specimen; Rhenish Mountains, Hasselbachtal ; Hangenberg Limestone , bed 49 ; Weyer 1993–1994 Coll.; MB.C.5236.1 • 1 specimen; Rhenish Mountains, Oese , old quarry ; Hangenberg Limestone , bed 30 ; Weyer & Korn 2000 Coll.; MB.C.5258.2 • 1 specimen; Rhenish Mountains, Oese , old quarry ; Hangenberg Limestone , bed 28 ; Weyer & Korn 2000 Coll.; MB.C.5260.4 • 1 specimen; Rhenish Mountains, Oese , old quarry ; bed interval VI ; Paproth Coll.; MB.C.5282.

Description

Holotype BGRB X5716 is a specimen with nearly 15 mm conch diameter and allows the examination of two whorls ( Fig. 110 View Fig ). It is thinly discoidal and subevolute (ww/dm = 0.42; uw/dm = 0.45) with a weakly depressed whorl profile (ww/wh = 1.28). The venter possesses two shallow longitudinal grooves with a rounded keel rising between them. On the last volution there are about 24 sharp ribs; these ribs form sharp nodes around the umbilicus and become weaker towards the flank. In the area of the outer flank they bend slightly forward and form a low projection before they diminish. Faint growth lines follow the course of the ribs; they form a low ventrolateral projection and a deep, broadly rounded ventral sinus. The penultimate whorl possesses 24 ribs.

The smaller, well-preserved specimen MB.C.31214.1 has a conch diameter of 14.5 mm and is also thinly discoidal and subevolute (ww/dm = 0.39; uw/dm = 0.43). In the sculpture it closely resembles the holotype; it has 26 ribs on the last and 24 ribs on the penultimate whorl ( Fig. 112A View Fig ). The ventral grooves are slightly deeper than in the holotype.

The incomplete ontogeny preserved in the sectioned specimen GPIT-PV-63982 shows a whorl profile that is, between 4 and 7.5 mm conch diameter, depressed crescent-shaped with a ww/wh ratio being reduced from 1.70 to 1.50. A raised ventral keel is present at 9.8 mm dm.

Larger specimens (e.g., specimens GPIT-PV-63978 and GPIT-PV-63980) show that the whorl profile becomes circular at 27 mm dm ( Fig. 111A–B View Fig ).

The growth trajectories are essentially consistent with those from the other representatives of the subfamily. Almost all trajectories are close to monophasic in the interval between 4 and 27 mm conch diameter with only minor changes of the conch ratios ( Fig. 112C–E View Fig ).

Remarks

Pseudarietites westfalicus differs from the very similar P. silesiacus in the lower number of ribs ( 25 in P. westfalicus but 30 in P. silesiacus ). Pseudarietites westfalicus can be separated from P. subtilis by the much wider umbilicus (uw/dm = 0.45 in P. westfalicus at 20 mm dm but about 0.35 in P. subtilis ).