Liroceratidae Miller & Youngquist, 1949

Family Liroceratidae Miller & Youngquist, 1949 View in CoL

Fig. 32 View Fig

Diagnosis

Family of the superfamily Liroceratoidea with a usually pachyconic or globular, 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 species, the venter can be flattened or concave in advanced species. Umbilical margin rounded; umbilical wall usually convex. Ornament usually consisting of fine growth lines; spiral lines occur in some genera. Septum simple in shape, concavely domed; suture line very simple, almost straight across flanks and venter or with small lobes and saddles.

Included genera

Solenoceras Hyatt, 1884 [homonym of Solenoceras Conrad, 1860 ; objective synonym of Coelogasteroceras ].

Coelogasteroceras Hyatt, 1893 (Bashkirian to Changhsingian; 11 species).

Coloceras Hyatt, 1893 [homonym of Coloceras Taschenberg, 1882 ; synonym of Liroceras ].

Stearoceras Hyatt, 1893 (Serpukhovian to Changhsingian; 10 species).

Peripetoceras Hyatt, 1894 (Serpukhovian to Changhsingian; 22 species).

Potoceras Hyatt, 1894 (? Viséan; 1 species).

Nannoceras Hyatt, 1894 [nomen nullum; synonym of Peripetoceras ].

Conradiceras Cossmann, 1900 [objective synonym of Coelogasteroceras ].

Cyclonautilus Hind, 1910 [synonym of Peripetoceras ].

Liroceras Teichert, 1940 (Viséan to Changhsingian; 47 species).

Condraoceras Miller, Lane & Unklesbay, 1947 (Kasimovian to Artinskian; 3 species).

Periptoceras Chao, 1954 [nomen nullum; synonym of Peripetoceras ].

Hemiliroceras Ruzhencev & Shimansky, 1954 (Bashkirian to Artinskian; 6 species).

Bistrialites Turner, 1954 (Viséan to Serpukhovian; 5 species).

Pseudophacoceras Turner, 1966 (? Viséan; 1 species).

Neobistrialites Tucker, Mapes & Aronoff, 1978 (Moscovian; 1 species).

Jianoceras Ma, 1997 (Permian; 1 species).

Nemdoceras Barskov & Shilovsky, 2014 (Roadian; 3 species).

Paraliroceras Barskov & Shilovsky, 2014 (Roadian to Changhsingian; 2 species).

Tatianautilus Barskov & Shilovsky, 2014 (Roadian; 1 species).

Leniceras Leonova & Shchedukhin, 2020 (Asselian or Sakmarian; 1 species).

Shikhanonautilus Leonova & Shchedukhin, 2020 (Asselian or Sakmarian; 1 species).

Thyoceras Leonova & Shchedukhin, 2020 (Asselian or Sakmarian; 1 species).

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

Perunautilus Crick & Sobolev, 1994 (Triassic).

Tomponautilus Sobolev, 1989 (Triassic).

Remarks

The Liroceratidae are probably the family with the longest stratigraphic range among the Palaeozoic Nautilida , extending from the Early Carboniferous to the Triassic. It can be regarded as a morphologically very stable clade in which morphological changes occurred only very rarely. Some of the new morphological developments have been separated as independent families ( Permonautilidae , Paranautilidae ), so that the Liroceratidae represent the conservative stem group.

The distribution of species among the 18 Palaeozoic genera within the Liroceratidae shows a very asymmetric picture. Nine genera are represented by only one species, while Liroceras and Peripetoceras are very diverse with 47 and 22 species, respectively. In addition, many species are known from only one specimen. As with many other groups of Nautilida , a revision is necessary and will probably change the picture so that fewer genera and species can be accepted.