Paragattendorfia sphaeroides Weyer, 1972

Korn, Dieter & Weyer, Dieter, 2023, The ammonoids from the Gattendorfia Limestone of Oberrödinghausen (Early Carboniferous; Rhenish Mountains, Germany), European Journal of Taxonomy 882, pp. 1-230 : 35-37

Paragattendorfia sphaeroides Weyer, 1972

Figs 22–23 ; Tables 12–13

Paragattendorfia sphaeroides Weyer, 1972: 340 .

Imitoceras globosum – Vöhringer 1960: 146, text-fig. 23.

Paragattendorfia sphaeroides – Korn 1994: 37, text-figs 31e, 32e–f, 33.

Diagnosis

Species of Paragattendorfia with a conch reaching 40 mm diameter. Conch at 20 mm dm thickly pachyconic, subinvolute (ww/dm ~0.80; uw/dm ~0.20). Whorl profile at 20 mm dm moderately depressed (ww/wh ~1.70); coiling rate very low (WER ~1.50). Venter broadly rounded, umbilical margin subangular. Growth lines fine, narrow-standing, with nearly linear course. Without constrictions on the shell surface; with linear internal shell thickenings. Suture line with narrowly V-shaped external lobe and very narrowly V-shaped adventive lobe.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 3c; Vöhringer Coll.; illustrated by Korn (1994: text-fig. 31e); re-illustrated here in Fig. 22 ; GPIT-PV- 63909 .

Paratypes

GERMANY • 2 specimens; Rhenish Mountains , Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 2; Vöhringer Coll.; GPIT-PV- 63935 , GPIT-PV- 63937 .

Description

Holotype GPIT-PV-63909 is a moderately preserved specimen with 22 mm conch diameter ( Fig. 22 ). It is a thickly pachyconic, subinvolute conch (ww/dm = 0.78; uw/dm = 0.20) with a narrowly rounded umbilical margin, steep umbilical wall and broadly and continuously rounded flanks and venter. The ornament consists of fine, closely spaced growth lines with an almost straight course ( Fig. 23D ).

The two sectioned paratypes GPIT-PV-63937 and GPIT-PV-63935 show almost identical cross-sectional patterns ( Fig. 23 A-B). The whorl profiles are rather similar in their crescent outline at all size stages larger than 6 mm conch diameter. However, particularly paratype GPIT-PV-63935 has a spindle-shaped juvenile stage at 3–5 mm conch diameter, in which the umbilical margin is slightly raised and the flanks are strongly divergent. The illustration of the ontogenetic trajectories shows a distinct allometry in the ww/dm ratio, and thus the ww/wh ratio ( Fig. 23 E-G).

The suture line of paratype GPIT-PV-63935 has a narrow V-shaped external lobe, a symmetrical ventrolateral saddle and a symmetrical V-shaped adventive lobe with slightly inwardly curved flanks ( Fig. 23C ).

Remarks

Paragattendorfia sphaeroides is separated from P. patens by the stouter conch (the ww/dm ratio is above 1.00 in P. sphaeroides but only ~ 0.85 in P. patens at 10 mm dm) and in the narrower umbilicus (uw/dm ~ 0.20 in P. sphaeroides but ~ 0.30 in P. patens at 10 mm dm).

Paragattendorfia sphaeroides differs from P. humilis from Upper Franconia in the course of the growth lines, which is nearly linear in P. patens but strongly convex in P. humilis .

Figures

Fig. 22. Paragattendorfia sphaeroides Weyer, 1972, from the Oberrödinghausen railway cutting, (Vöhringer Coll.), holotype GPIT-PV-63909 from bed 3c. Scale bar units =1 mm.

Fig. 23. Paragattendorfia sphaeroides Weyer, 1972 from the Oberrödinghausen railway cutting. A. Cross section of paratype GPIT-PV-63937 from bed 2. B. Cross section of paratype GPIT-PV-63935 from bed 2. C. Suture line of paratype GPIT-PV-63935 from bed 2, at ww = 13.2 mm, wh =6.0 mm. D. Growth line course of holotype GPIT-PV-63909 from bed 3c, at dm =22.0 mm, ww = 17.5 mm, wh= 11.5 mm. E –G. Ontogenetic development of the conch width index (ww/dm), umbilical width index (uw/dm), whorl width index (ww/wh) and whorl expansion rate (WER) of selected specimens. Scale bar units= 1 mm.