Family Domatoceratidae Miller & Youngquist, 1949

Figs 18A–B – 19

Diagnosis

Family of the superfamily Grypoceratoidea with a thinly to thickly discoidal, subinvolute to evolute conch. Whorl profile in the adult stage usually compressed subquadrate or inverted trapezoidal. Umbilical margin distinct or sharp; ventrolateral shoulder nearly rectangular to broadly rounded, rarely skid-like. Ornament consisting of fine growth lines; some species have tubercles on the ventrolateral shoulder. Suture line always with rounded but distinct external, lateral and internal lobes separated by a narrowly rounded or subacute saddles; without annular process.

Included genera

Pselioceras Hyatt, 1884 (Wuchiapingian to Changhsingian; 3 species).

Titanoceras Hyatt, 1884 (Virgilian; 2 species).

Domatoceras Hyatt, 1891 (Moscovian to Changhsingian; 38 species).

Pseudometacoceras Miller, Dunbar & Condra, 1933 [synonym of Domatoceras Hyatt, 1891]. Paradomatoceras Delépine, 1937 (Bashkirian; 1 species).

Plummeroceras Kummel, 1953 (Artinskian; 1 species).

Neodomatoceras Ruzhencev & Shimansky, 1954 (Artinskian; 2 species).

Parapenascoceras Ruzhencev & Shimansky, 1954 (Kasimovian to Roadian; 7 species).

Penascoceras Ruzhencev & Shimansky, 1954 (Kungurian to Roadian; 3 species).

Permodomatoceras Ruzhencev & Shimansky, 1954 (Artinskian to Wuchiapingian; 6 species). Stenodomatoceras Ruzhencev & Shimansky, 1954 (Kasimovian; 4 species).

Virgaloceras Schindewolf, 1954 (Changhsingian; 1 species).

Neostenopoceras Zhao, Liang & Zheng, 1978 (Changhsingian; 1 species).

Shatoceras Leonova & Shchedukhin, 2020 (Asselian; 1 species).

Omorphoceras Leonova & Shchedukhin, 2023 (Asselian or Sakmarian; 1 species).

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

Remarks

As with other families of Carboniferous and Permian nautilids, the justification and content of the family Domatoceratidae has been the subject of much debate; the views of the various authors were differing widely. When first described, Miller & Youngquist (1949) placed the five genera Domatoceras, Pselioceras, Stearoceras Hyatt, 1893, Stenopoceras and Titanoceras in the family Domatoceratidae. Kummel (1953) did not accept the family and synonymised it with the family Grypoceratidae. Moreover, he even considered Domatoceras to be a subgenus of Grypoceras. The genera and subgenera included by him in the Grypoceratidae were Grypoceras (Grypoceras), Grypoceras (Domatoceras), Grypoceras (Plummeroceras), Gryponautilus Mojsisovics, 1902, Stenopoceras, Menuthionautilus Collignon, 1933, Stearoceras, Titanoceras and Pselioceras.

Ruzhencev & Shimansky (1954) discussed the taxa belonging to this group in detail and included the four already known genera Domatoceras, Titanoceras, Pselioceras and Stenopoceras as well as the six newly named genera Penascoceras, Parapenascoceras, Permodomatoceras, Neodomatoceras, Stenodomatoceras and Parastenopoceras Ruzhencev & Shimansky, 1954. In the Osnovy (Shimansky 1962), the group was listed only as a subfamily within the family Grypoceratidae. In addition to the ten genera already mentioned, Paradomatoceras, Plummeroceras (as a subgenus of Domatoceras), Virgaloceras and Menuthionautilus were also included, the latter being the only Triassic genus.

In the Treatise, Kummel (1964) reiterated his previously published view and did not accept the Domatoceratidae as a valid family. He considered the genera Stenodomatoceras, Penascoceras and Permodomatoceras newly named by Ruzhencev & Shimansky (1954) to be synonyms of Domatoceras and Parapenascoceras and Neodomatoceras as synonyms of Stearoceras. He included the genus Epidomatoceras in the family Grypoceratidae.

Sobolev (1989) did not accept the independence of a family Domatoceratidae either and included the corresponding genera in the family Grypoceratidae. However, he accepted the validity of the Permian genera named by Ruzhencev & Shimansky (1954) but did not include Epidomatoceras in the family.

As in other Carboniferous–Permian nautilid families, the possible phylogenetic and systematic relationships in the Domatoceratidae (or Grypoceratidae) have been intensively discussed. Ruzhencev & Shimansky (1954) followed the concept that the systematics should be based on phylogeny; they therefore divided the family into a number of genera according to hypothetical evolutionary lineages. This contrasted sharply with other approaches, such as that of Kummel (1953: 45), who had stated: “As an evolutionary unit this family appears to be closely integrated. The extensive variations experimented with in this family keep an over-all unity in both the shape of the conch and sutural development.” As a consequence, Kummel (1964) distinguished considerably fewer independent genera than Ruzhencev & Shimansky (1954) and Shimansky (1962).

A reconstruction of the phylogeny was undertaken by Dzik (1984). He derived the species of the family Domatoceratidae (which he included in the Grypoceratidae) from the Early Carboniferous genus Epidomatoceras and subdivided it into several long-ranging evolutionary lineages extending from the Carboniferous to the Triassic. Contrary to earlier concepts (Shimansky 1957; Kummel 1964), he placed Germanonautilus in the evolutionary lineage of Titanoceras and the Syringonautilidae Mojsisovics, 1902 in the lineage of Domatoceras. According to this reconstruction, Stenopoceras is separated from the Grypoceratidae and is considered a descendant of Phacoceras in the family Phacoceratidae.

An unanswered question is still whether certain morphological variations within the family Domatoceratidae occurred only once or iteratively. These characters include (1) the formation of a concave venter, (2) the formation of an angular ventrolateral margin and ventrolateral skids, (3) the formation of an angular umbilical margin, (4) the narrowing (but also widening) of the umbilicus, (5) the change to more compressed or depressed whorl profiles and (6) the development of ventrolateral tubercles. For example, it is not clear whether the separation of the genera Stenodomatoceras and Permodomatoceras from Domatoceras, which was justified by the reduction in umbilical width and whorl height, respectively, actually occurred only once. Therefore, it is not possible to say with certainty whether these genera are monophyletic units.