Zadelsdorfia oblita, Korn & Weyer, 2023

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 : 143-144

Zadelsdorfia oblita sp. nov.

urn:lsid:zoobank.org:act:97D9ABF0-4091-47B6-B631-F2B1DA85452D

Fig. 86 ; Table 80

Diagnosis

Species of Zadelsdorfia with a conch reaching 50 mm diameter. Conch at 30 mm dm thinly pachyconic, subinvolute (ww/dm ~0.70; uw/dm ~0.30). Whorl profile in the juvenile stage crescent-shaped, at 30 mm dm moderately depressed (ww/wh ~1.75); coiling rate low (WER ~1.60). Venter broadly rounded, umbilical margin narrowly rounded. Growth lines fine, wide-standing, with concavo-convex course. Weak constrictions on the shell surface and prominent internal shell thickenings; sharp, short ribs and coarse spiral lines on the inner flank.

Etymology

From the Latin ‘ oblita ’ = ‘forgotten’; because of the undescribed material in the Vöhringer collection.

Material examined

Holotype

GERMANY • Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 1; Vöhringer Coll.; illustrated in Fig. 86 ; MB.C.31174.1.

Paratypes

GERMANY • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 1; Vöhringer Coll.; MB.C.31174.2–3 .

Description

Holotype MB.C.31174.1 is a specimen that was already sectioned by Vöhringer, but no inner whorls are preserved ( Fig. 86 ). The specimen has a diameter of 33 mm and is thinly pachyconic and subinvolute (ww/dm = 0.69; uw/dm = 0.29) with a rounded umbilical margin, a convex umbilical wall and broadly rounded flanks and venter. The specimen shows moderately well preserved shell remains that appear largely smooth. Weak spiral lines are visible on the flank; they cross the fine, wide-standing growth lines. The shell surface shows a concavo-convex constriction forming a shallow lateral sinus, a distinct ventrolateral projection and a moderately deep ventral sinus.

Remarks

Specimens of the new species were placed in Gattendorfia costata by Vöhringer (1960). However, clear differences are present: The holotype of G. costata has a rather wide umbilicus with a uw/dm ratio of 0.44 at 32 mm dm, while in Zadelsdorfia oblita sp. nov. it is only 0.29. Furthermore, G. costata has a pronounced umbilical margin, which is rounded in Z. oblita .

Zadelsdorfia oblita sp. nov. differs from all other species of the genus known from the Hangenberg limestone of Oberrödinghausen by the combination of a pachyconic conch and internal shell thickenings, which show a distinct concavo-convex course. Another characteristic to distinguish Z. oblita from the other species is the presence of spiral lines.

Figures

Fig. 86. Zadelsdorfia oblita sp. nov. from the Oberrödinghausen railway cutting; photographs and dorsal view reconstruction of holotype MB.C.31174.1 (Vöhringer Coll.) from bed 1. Scale bar units =1 mm.