Permonautilidae Barskov & Shilovsky, 2014

Family Permonautilidae Barskov & Shilovsky, 2014

Fig. 34 View Fig

Diagnosis

Family of the superfamily Liroceratoidea with a pachyconic or globular, usually subinvolute to subevolute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter form a continuous arch in the early forms, the venter can be flattened or concave in advanced forms. Terminal aperture with long lateral shell processes emerging from the umbilical margin. Ornament consisting of fine or coarse growth lines. Septum simple in shape, concavely domed; suture line very simple, almost straight across flanks and venter or with small lobes and saddles.

Included genera

Permonautilus Kruglov, 1933 (Roadian to Wuchiapingian; 10 species).

Alexandronautilus Shimansky, 1962 [synonym of Permonautilus Kruglov, 1933 ].

Remarks

The family Permonautilidae was introduced by Barskov & Shilovsky in Barskov et al. (2014) on the basis of virtually one character to separate it from the Liroceratidae , namely the presence of long lateral shell processes emerging from the umbilical margin. Such a process is apparently absent in the other genera of the superfamily Liroceratoidea . Very similar processes are only known from the family Solenochilidae (suborder Solenochilina ), which is not related to the Permonautilidae . Barskov & Shilovsky in Barskov et al. (2014: 1391) clarified that the Permonautilidae are separated from the Solenochilidae by the position of the siphuncle, which is subcentral or centrodorsal in the Permoceratidae and subventral in the Solenochilidae .

The occurrence of the long shell processes in the Early to Late Carboniferous Solenochilidae and the Middle to Late Permian Permonautilidae is indeed a very interesting phenomenon, as both families belong to two unrelated evolutionary lineages that were probably separated already in the Devonian ( Dzik 1984). Although the distinction between the two families Liroceratidae and Permonautilidae is based on only one character, the separation is still accepted here with reservations.

New family Korn & Ghaderi (in press)

Fig. 35 View Fig

Diagnosis

Family of the superfamily Liroceratoidea with a usually pachyconic, subinvolute to involute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter usually separated by distinct ventrolateral shoulder, venter or concave. Umbilical margin subangular or angular; umbilical wall steep, flattened. Ornament usually consisting of fine growth lines. Septum simple in shape, concavely domed; suture line with shallow lobes on venter and flank (from Korn & Ghaderi in press: 98).

Included genera

New genus H to be described by Korn & Ghaderi (in press) (Changhsingian; 2 species).

New genus E to be described by Korn & Hairapetian (in press) (Wuchiapingian; 2 species).

New genus F to be described by Korn & Hairapetian (in press) (Wuchiapingian; 1 species).

Remarks

The new family is characterised by a combination of characters not found in any other family of Palaeozoic nautilids. This is the combination of a rather stout conch with a very pronounced umbilical margin and also a sometimes pronounced ventrolateral shoulder. While the first character suggests a placement in the superfamily Liroceratoidea , the second and third characters show a closer morphological relationship to the superfamilies Pleuronautiloidea and Grypoceratoidea . Unfortunately, the early ontogenetic development of the conch in the species of the new family is not known. However, the material shows that the pronounced umbilical margin is present early in ontogeny and that this feature can therefore be considered apomorphic, whereas the ventrolateral shoulder does not assume a subangular shape until a late ontogenetic stage, if at all. Therefore, these genera are included here as a new family of the superfamily Liroceratoidea (from Korn & Ghaderi in press: 98).