Tainoceratina Shimansky, 1957

Suborder Tainoceratina Shimansky, 1957

Fig. 23 View Fig

Diagnosis

Suborder of the order Nautilida , in which a ventrolateral shoulder and an umbilical margin are formed early in ontogeny in the advanced species. Conch usually discoidal, subinvolute to evolute. Juvenile whorl profile depressed oval or circular. Adult whorl profile depressed oval or reniform in the early species, showing numerous modifications during evolution (inverted trapezoidal, trapezoidal or polygonal whorl profiles or with ventral depression). Dorsal whorl zone always present, but usually very small. Juvenile sculpture with radial ribs on the flank; adult sculpture with radial ribs on the flank, ventrolateral nodes or several rows of nodes in derived species. Septa simply domed, with dorsal inflexion in advanced species. Suture line depending on the whorl profile, with shallow lobes and low saddles. Siphuncle in central or subcentral position.

Included superfamilies

Tainoceratoidea Hyatt, 1883 (Late Carboniferous to Early Triassic; 23 Palaeozoic genera, 89 Palaeozoic species).

Pleuronautiloidea Hyatt, 1900 (Late Carboniferous to Late Triassic; 32 Palaeozoic genera, 190 Palaeozoic species).

Remarks

Taxonomy

A number of different concepts have been published with regard to the taxonomic composition and subdivision of the Tainoceratina . In the concept used here and in contrast to earlier authors, the suborder Tainoceratina is more restricted in size and several taxa of different rank are excluded, such as the Rutoceratidae , the Temnocheilidae and the Koninckioceratidae . Accordingly, the stratigraphic range of the suborder Tainoceratina is considered here from Viséan to Triassic.

Morphology and subdivision

The phylogenetic scheme proposed by Shimansky (1957, 1962) distinguished four evolutionary lineages, translated in superfamilies within the suborder Tainoceratina : Tainocerataceae Hyatt, 1883 , Encoilocerataceae Shimansky & Erlanger, 1955 , Temnocheilaceae Mojsisovics, 1902 and Rhiphaeocerataceae Ruzhencev & Shimansky, 1954 . According to this scheme, the clade consisting of the superfamilies Tainocerataceae and Encoilocerataceae and the clade consisting of the families Gzheloceratidae Ruzhencev & Shimansky, 1954 , Rhiphaeoceratidae Ruzhencev & Shimansky, 1954 and Aktubonautilidae Ruzhencev & Shimansky, 1954 are monophyletic, respectively.

Kummel (1964) included the families Rutoceratidae , Tetragonoceratidae , Tainoceratidae , Rhiphaeoceratidae and Koninckioceratidae in the Tainocerataceae and postulated a Devonian to Triassic range for the superfamily. For the three superfamilies Aipocerataceae , Trigonocerataceae and Clydonautilaceae , he did not provide a clear phylogenetic hypothesis of origin, but suggested that they, like the tainoceratids, were derived from the Rutoceratidae or another ancestral family in the Devonian.

Dzik (1984) used the suborder Tainoceratina for practical reasons to include almost all Late Palaeozoic and Triassic nautiloids; he did not distinguish superfamilies, but rather separated the families Trigonoceratidae , Tainoceratidae , Grypoceratidae , Clydonautilidae , Syringonautilidae and Liroceratidae . It is worth noting that he only included post-Devonian taxa in the Tainoceratina .

Here, the suborder Tainoceratina is reduced to include only the superfamilies Tainoceratoidea and Pleuronautiloidea . This classification is based on phylogenetic considerations based on some key morphological characters. A common morphological feature of the two superfamilies is the early ontogenetic development of both a subangular ventrolateral shoulder and a subangular umbilical margin in the advanced species ( Fig. 3D, I View Fig ). Radial ribs appear in the juvenile conch within several lineages. The general shape of the conch is discoidal and subevolute; subinvolute and evolute conchs are an exception. Tainoceratids are very conservative in this respect; Carboniferous, Permian and Triassic species can have very similar conch morphologies, but the latter probably regularly possess a dorsal inflexion of the septum, causing an annular process.

The two superfamilies are characterised by the following main morphological features:

Tainoceratoidea . – Forms with usually octagonal whorl profile with a more or less deep mid-ventral longitudinal groove; sculpture usually with several rows of nodes ( Fig. 23A View Fig ).

Pleuronautiloidea . – Forms with usually quadrate, trapezoidal or inverted trapezoidal whorl profile with a more or less strongly flattened venter; sculpture usually with ventrolateral nodes and ribs on the flank, sometimes with more or less long spines ( Fig. 23B View Fig ).

Origin

The origin of the suborder Tainoceratina (as interpreted here) is not completely resolved. Ruzhencev & Shimansky (1954) saw the origin of the tainoceratids (in a more general view) in the Devonian family Tetragonoceratidae Flower, 1945 and derived the Tainoceratina from the family Rutoceratidae Hyatt, 1884 . Shimansky (1967: 39) stated that the family Gzheloceratidae , which was considered to be the ancestral family from which the family Tainoceratidae and others were derived, arose directly from the family Rutoceratidae .

Dzik (1984: 160) proposed an alternative origin for the tainoceratids. Most importantly, he proposed parallel evolutionary lineages within the group, here separated as the superfamilies Tainoceratoidea and Pleuronautiloidea . Dzik associated Tainoceras Hyatt, 1883 with the Viséan to Serpukhovian genus Tylonautilus Pringle & Jackson, 1928 , which like Tainoceras has a polygonal whorl profile with a midventral groove and a sculpture with ribs and rows of nodules or tubercles. This hypothesis would imply a Bashkirian to early Gzhelian interval between the last occurrence of the ancestor Tylonautilus and the first of the descendant Tainoceras . Dzik also formulated the hypothesis that Tylonautilus was derived from the Viséan genus Celox Shimansky, 1967 .

Dzik saw the origin of the group described here as Pleuronautiloidea in Early Carboniferous representatives of the genus Gzheloceras Ruzhencev & Shimansky, 1954 , which are now attributed to Pseudogzheloceras Dernov, 2021 ( Dernov 2021). According to this hypothesis ( Dzik 1984: 160), Gzheloceras should be derived from the genus Celox , which in turn should have been derived from the Tournaisian to Viséan genus Vestinautilus . This would mean that the superfamilies Tainoceratoidea Hyatt, 1883 and Pleuronautiloidea Hyatt, 1900 have a common ancestor in the genus Celox . At the same time, it means that the angular umbilical margin was acquired independently later in the evolution of the two superfamilies.

This hypothesis for the origin of the tainoceratids in the strict sense, formulated by Dzik (1984), seems to be the most plausible in view of the available data. Within the genus Vestinautilus and closely related genera, the transition from the Tournaisian to the Viséan was marked by a progressive simplification of shell ornamentation, with the loss of the original spiral ridges and the strongly pronounced ventrolateral shoulder. Such a morphological trend including the new formation of lateral ribs could have led to genera such as Celox and Pseudogzheloceras .

As an alternative to a phylogenetic origin in the genus Vestinautilus , the tainoceratids could be derived from originally more evolute and discoidal species. Representatives of the family Subclymeniidae , in particular the genera Maccoyoceras and Epidomatoceras , are possible candidates. This would mean that the Tainoceratina and Domatoceratina subordo nov. are largely sister groups.

Phylogeny

Dzik (1984: text-fig. 62) drew a complex system of relationships with a number of parallel evolutionary lineages within the group, the most important of which are:

(1) Gzheloceras – Pleuronautilus : this evolutionary lineage already began in the Early Carboniferous with Pseudogzheloceras memorandum Shimansky, 1967 and continued through the Late Carboniferous and Permian with species of Pseudogzheloceras and Gzheloceras . In the Early Permian, this lineage included species now classified as Pseudofoordiceras Ruzhencev & Shimansky, 1954 . According to this phylogenetic reconstruction, a separate lineage continued into the Triassic and was represented by Pleuronautilus trinodosus Mojsisovics, 1882 and other species of the same genus.

(2) Gzheloceras – Metacoceras dorashamense , M. dorsoarmatum – Pleuronautilus pichleri : this evolutionary lineage began in the Bashkirian with Pseudogzheloceras faticatum Shimansky, 1967 and continued into the Permian via P. tacitum Shimansky, 1967 (Moscovian) and P. maklai Shimansky, 1967 (Kasimovian). From the Wuchiapingian, the species “ Metacoceras dorashamense ”, “ M. dorsoarmatum ” and “ Pleuronautilus dzhulfensis ” belong in this lineage. Survivors into the Triassic formed the species Pleuronautilus pichleri author+year and the genera Encoiloceras Hyatt, 1900 and Anoploceras Hyatt, 1900 .

(3) Pseudotemnocheilus – Tirolonautilus : this evolutionary lineage began in the Moscovian with Temnocheiloides acanthicus (Tzwetaev, 1888) and continued in the Permian with Pseudotemnocheilus Ruzhencev & Shimansky, 1954 and Tirolonautilus Mojsisovics, 1902 . Two side branches were represented by Cooperoceras Miller, 1945 and Articheilus Ruzhencev & Shimansky, 1954 , respectively.

(4) Metacoceras – Enoploceras , Mojsvaroceras : this evolutionary lineage began in the Kasimovian with Metacoceras mcchesneyi Murphy, 1970 and continued throughout the Permian. In the Triassic there was a diversification into different genera ( Enoploceras Hyatt, 1900 , Mojsvaroceras Hyatt, 1883 ).