Paragattendorfia Schindewolf, 1924

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 : 10-11

Genus Paragattendorfia Schindewolf, 1924

Type species

Paragattendorfia humilis Schindewolf, 1924 ; original designation.

Diagnosis

Genus of the subfamily Prionoceratinae with a pachyconic to globular conch in the juvenile and adult stage. The umbilicus opens stepwise during ontogeny, the umbilical width ratio remains nearly constant throughout ontogeny. Shell with fine to lamellar, convex or straight growth lines. External lobe and adventive lobe V-shaped.

Genus composition

Central Europe ( Schindewolf 1924; Vöhringer 1960; Weyer 1972): Paragattendorfia humilis Schindewolf, 1924 ; Imitoceras patens Vöhringer, 1960 ; Paragattendorfia sphaeroides Weyer, 1972 .

North Africa ( Bockwinkel & Ebbighausen 2006): Paragattendorfia aboussalamae Bockwinkel & Ebbighausen, 2006 .

Central Asia ( Librovitch 1940): Gattendorfia applanata Librovitch, 1940 ; Gattendorfia kazakhstanica Librovitch, 1940 ; Gattendorfia occlusa Librovitch, 1940 ; Gattendorfia reticulata Librovitch, 1940 .

South China ( Ruan 1981): Imitoceras (Imitoceras) subpatens Ruan, 1981 ; Imitoceras (Imitoceras) globoidale Ruan, 1981 .

Remarks

Several species were placed in the genus Paragattendorfia since its revision by Weyer (1972). However, Paragattendorfia was a somewhat problematic genus. It was inadequately defined by Schindewolf (1924) and insufficiently characterised by the statement that “with a general similarity of shape to Gattendorfia , it only differs from the latter in that the lateral lobe lies on the seam and not next to it as in Gattendorfia ”. Furthermore, the inner lobe elements should be very narrow and deep; the growth lines should be linear without ventral sinus and constrictions were not seen.

With the redescription and diagnosis of the type species P. humilis , Paragattendorfia can be stabilised as a genus belonging to the subfamily Prionoceratinae because of the globular conch geometry, the low aperture throughout ontogeny and the rather simple ontogenetic pathways ( Korn & Weyer 2023).

Paragattendorfia is unique among the prionoceratids of the Early Tournaisian in its stepwise opening of the umbilicus, meaning than the uw/dm trajectory is nearly isometric. In this respect, it can easily be separated from Mimimitoceras , which may have a similar morphology in distinct growth stages, but possesses an involute adult conch.

Stratigraphic range

In the Rhenish Mountains, the two species P. patens and P. sphaeroides only occur in the higher part of the Hangenberg Limestone ( Pseudarietites westfalicus Zone and Eocanites delicatus Zone ). At Gattendorf, however, no ammonoids are known from beds higher than the Acutimitoceras acutum Zone , hence the genus has a duration throughout the “ Gattendorfia Stufe ”. The species described from Kazakhstan ( Librovitch 1940) have possibly a middle Tournaisian age.