Pleuronautilidae Hyatt, 1900

Korn, Dieter, 2025, A revised classification of the Carboniferous and Permian Nautilida, European Journal of Taxonomy 1017, pp. 1-85 : 57-59

Family Pleuronautilidae Hyatt, 1900

Fig. 29

Diagnosis

Family of the superfamily Pleuronautiloidea with a commonly subquadrate or weakly depressed whorl profile; venter ranging from convex to weakly concave, ventrolateral shoulder and umbilical margin often pronounced, flanks usually weakly convergent. Sculpture with numerous ribs on the flank, sometimes with conical tubercles and more rarely with spiral ridges. An annular process is present in the advanced species.

Included genera

New genus C to be described by Korn & Hairapetian (in press) (Wordian to Changhsingian; 10 species). Pleuronautilus Mojsisovics, 1882 (Triassic).

Phloioceras Hyatt, 1884 (Triassic).

Anoploceras Hyatt, 1900 (Triassic).

Encoiloceras Hyatt, 1900 (Triassic).

Enoploceras Hyatt, 1900 (Triassic).

Holconautilus Mojsisovics, 1902 (Triassic).

Trachynautilus Mojsisovics, 1902 (Triassic).

Sibyllonautilus Diener, 1915 (Triassic).

Phaedrysmocheilus Shimansky & Erlanger, 1955 (Triassic).

Arctonautilus Sobolev, 1989 (Triassic).

Grumantoceras Sobolev, 1989 (Triassic).

Remarks

Pleuronautilus is a genus that has been the subject of very different opinions in the literature over the last few decades. The genus was established by Mojsisovics (1902) for the very distinctive Triassic species Pleuronautilus trinodosus . von Arthaber (1900: 215) also used the genus name for the Late Permian forms similar to the species “ Nautilus dorso armatus ” that was described by Abich (1878) and his newly established species “ Pleuronautilus Verae ”; he considered both to be closely related.

While Miller & Youngquist (1949) did not use the genus name Pleuronautilus for Permian nautilids, Kummel (1953: 34) placed 24 Permian species in this genus, together with 34 Triassic species. The reason for this high number is that Kummel also included a number of species in Pleuronautilus that had previously been placed in other genera ( Metacoceras , Foordiceras , Huanghoceras ).

Ruzhencev & Shimansky (1954) reduced the species composition of Pleuronautilus by accepting the genera Huanghoceras and Shansinautilus and by establishing the new genus Pseudofoordiceras for some species from the Leonard Formation of Texas, which were previously placed in the genus Metacoceras by Miller (1945) and in Foordiceras by Miller & Youngquist (1949). However, Shimansky (1967) considered these three genera as being synonyms of Pleuronautilus ; he listed 19 species belonging to this genus. Kummel (1964), in the Treatise on Invertebrate Paleontology, had already before synonymised the genera Huanghoceras , Shansinautilus , Tungkuanoceras , Basleonautilus and Pseudofoordiceras with Pleuronautilus .

It has already been suggested by previous authors that it is difficult to distinguish clearly between genera such as Metacoceras and Pleuronautilus in the Permian nautiloid assemblages as interpreted at that time (e.g., Kummel 1953: 34). To ensure a monophyletic definition of Pleuronautilus and related genera, it is necessary to investigate the possible phylogenetic origin of these genera and their relationships. It also needs to be clarified whether species with Pleuronautilus -like conch morphology and sculpture, such as the recently described Late Permian Serometacoceras and Lutonautilus, could have evolved independently during the Permian.

Earlier authors had already considered that, starting from the putative ancestral genus Metacoceras , lateral branches with strengthened sculpture gave rise to several genera with coarse sculpture, such as Huanghoceras from the Taiyuan Series of North China ( Yin 1933) and Pseudofoordiceras from the Leonard Formation of Texas ( Ruzhencev & Shimansky 1954). Apparently, such considerations have not yet been made for the Late Permian species of the Transcaucasus. Both Shimansky (1965) and Teichert & Kummel (1973) assigned the species of this group of species to the two genera Metacoceras and Pleuronautilus . Such a practice would imply that the latter genus actually has a Late Permian origin. However, the empirical data is hardly sufficient for such a statement.

Here, the family Pleuronautilidae is reduced in its content to the Triassic species, which share some morphological characteristics, such as the rather dense transverse ribbing. Furthermore, they could be united by the presence of an annular process of the suture line, which means that they have a dorsal inflexion of the septum.

There are some Late Permian species that have a very similar shell and sculpture to Pleuronautilus , but the apparent lack the annular process. These will shortly be described as new genus C by Korn & Hairapetian (in press) and may be the ancestors of the Triassic pleuronautilids.

Figures

Fig. 29. Family Pleuronautilidae Hyatt, 1900. New species to be described by Korn & Hairapetian (in press); lateral and dorsal views, reconstruction of apertural view, from Korn & Hairapetian (in press). Scale bar units = 1 mm.