Gattendorfia Schindewolf, 1920

Korn, Dieter & Weyer, Dieter, 2023, The ammonoids from the Gattendorfia Limestone of Gattendorf (Devonian-Carboniferous boundary; Upper Franconia, Germany), European Journal of Taxonomy 883, pp. 1-61 : 47-48

Genus Gattendorfia Schindewolf, 1920

Type species

Goniatites subinvolutus Münster, 1839, p. 23 ; original designation.

Diagnosis

Genus of the Gattendorfiinae with discoidal to pachyconic conchs with low to moderately high coiling rate (WER =1.50–1.90); inner whorls subevolute to evolute, adult stage subevolute to evolute. Ornament with convex or slightly biconvex, rursiradiate growth lines, shell with or without constrictions. Suture line with deep, lanceolate external lobe; adventive lobe usually symmetric.

Genus composition

Central Europe ( Münster 1839b; Schindewolf 1924, 1952; Vöhringer 1960): Goniatites subinvolutus Münster, 1839 ; Gattendorfia ventroplana Schindewolf, 1924 [synonym of Gattendorfia subinvoluta ]; Gattendorfia tenuis Schindewolf, 1952 ; Gattendorfia costata Vöhringer, 1960 ; Gattendorfia rhenana Korn & Weyer, 2023 ; Gattendorfia bella Korn & Weyer, 2023 ; Gattendorfia valdevoluta Korn & Weyer, 2023 ; Gattendorfia schmidti Korn & Weyer, 2023 ; Gattendorfia corpulenta Korn & Weyer, 2023 ; Gattendorfia immodica Korn & Weyer, 2023 .

Remarks

Gattendorfia and Zadelsdorfia are closely related genera and it is not easy to separate them clearly. This is mainly because the ontogeny of many species is poorly known. Both genera contain species that have a more or less widely opened umbilicus even in the adult stage. The juvenile and preadult stages are usually evolute, while the uw/dm ratio can range between 0.20 and 0.50 in the adult stage among the species. The species of Gattendorfia and Zadelsdorfia can be subdivided into different groups with their characteristics such as conch shape (slender – stout), adult umbilical width (low – high), shape of the umbilical margin (rounded – subangular – angular), shell constrictions (absent – convex – concavoconvex) and growth lines (fine – lamellar). There is no obvious covariation of these characters. It is easiest to group the species according to the ww/dm and uw/dm ratios in the adult stage:

(1) Forms with discoidal conch shape and moderately wide umbilicus in the adult stage: G. subinvoluta , G. rhenana , G. schmidti .

(2) Forms with discoidal conch shape and wide umbilicus in the adult stage: G. bella , G. valdevoluta .

(3) Forms with pachyconic conch shape and wide umbilicus in the adult stage: G. costata , G. immodica .

(4) Forms with pachyconic to globular conch shape and moderately wide umbilicus in the adult stage: Z. crassa , Z. oblita .

The genus Zadelsdorfia was proposed by Weyer (1972) with the type species Gattendorfia asiatica Librovitch, 1940 ; it was introduced to include gattendorfiid ammonoids with a pouched external lobe. At the time it seemed to be restricted to the Middle Tournaisian, but in the meantime it has been demonstrated that Early Tournaisian species, among them G. crassa and several North African species, also possess a pouched external lobe (Korn 1994; Bockwinkel & Ebbighausen 2006; Ebbighausen & Bockwinkel 2007).

Korn & Feist (2007) regarded Zadelsdorfia as a junior synonym of Gattendorfia . However, it appears to be justified to separate the two genera on the basis of the shape of the external lobe (lanceolate in Gattendorfia but pouched in Zadelsdorfia ) and the conch ontogeny ( Gattendorfia has a widely umbilicate conch in adulthood, while in Zadelsdorfia the umbilicus is narrow in the adult stage). Furthermore, the adventive lobe tends to be asymmetric in Zadelsdorfia , while it is almost symmetric in Gattendorfia .

Bockwinkel & Ebbighausen (2006) separated the group of “ Gattendorfia molaris ” as an independent genus Weyerella . Gattendorfia differs from Weyerella primarily in the size of the conch, which in Gattendorfia reaches more than 50 mm diameter, while conchs of Weyerella usually do not exceed 25 mm.Another distinguishing feature is the width of the umbilicus in the juvenile stage; in Gattendorfia the umbilicus is very wide (> 0.55 of the diameter), whereas the uw/dm ratio in Weyerella only reaches a maximum of 0.50. According to Bockwinkel & Ebbighausen (2006), “ Weyerella differs from typical Gattendorfia in the mode of umbilicus, closing with an overlap of the whorls over the preceding and in the platyconic conch shape of the adult conch.”