Peripetoceras Hyatt 1894

Genus Peripetoceras Hyatt, 1894 Type species Nautilus Freieslebeni Geinitz, 1843; original designation. Diagnosis Genus of the family Liroceratidae with pachyconic or rarely globular, involute or subinvolute conch. The conch is rapidly increasing in height with a very high to extremely high coiling rate (WER usually 2.40– 3.00). Whorls weakly embracing with nearly circular profile in the juvenile stage and with a flattened venter in the adult stage. Adult ornament very weak. Septa without inflexions, slightly concave. Suture line nearly straight to straight with shallow lobes. Included Carboniferous species North America (Gordon 1960, 1965; Tucker & Mapes 1978; Tucker et al. 1978; Niko & Mapes 2015, 2017): Peripetoceras whitei Gordon, 1960, Bashkirian, Indiana; Peripetoceras ozarkense Gordon, 1965, Serpukhovian, Arkansas; Peripetoceras bridgeportense Tucker & Mapes, 1978, Kasimovian, Texas; Peripetoceras wewokense Tucker, Mapes & Aronoff, 1978, Moscovian, Oklahoma; Peripetoceras milleri Niko & Mapes, 2015, Serpukhovian, Arkansas; Peripetoceras kummeli Niko & Mapes, 2017, Serpukhovian, Arkansas. British Isles (Hind 1910; Bisat 1930): Cyclonautilus umbilicatus Hind, 1910, Bashkirian, Lancashire; Peripetoceras dubium Bisat, 1930, Bashkirian, Wales. South Urals (Shimansky 1967): Peripetoceras cautum Shimansky, 1967, Serpukhovian. Western Russia (Shimansky 1967): Peripetoceras globatoides Shimansky, 1967, Serpukhovian; Peripetoceras tormentum Shimansky, 1967, Serpukhovian; Peripetoceras fischeri Shimansky, 1967, Moscovian. Included Permian species Central Europe (Geinitz 1841; King 1850; Prinoth & Posenato 2007): Nautilus Freieslebeni Geinitz, 1843, Wuchiapingian, Saxony; Nautilus bowerbankianus King, 1850, Wuchiapingian, England [synonym of Peripetoceras freieslebeni (Geinitz, 1843)]; Peripetoceras comploji Prinoth & Posenato, 2007, Changhsingian, Dolomites; Peripetoceras gigas Prinoth & Posenato, 2007, Changhsingian, Dolomites. West Russia and Urals (Ruzhencev & Shimansky 1954; Barskov et al. 2014): Peripetoceras asselense Ruzhencev & Shimansky, 1954, Artinskian, South Urals; Peripetoceras ideliense Barskov & Shilovsky in Barskov et al., 2014, Roadian, West Russia; Peripetoceras burovi Barskov & Shilovsky in Barskov et al., 2014, Roadian, West Russia. NW Iran (this paper): Peripetoceras parum sp. nov., Wuchiapingian. Indopacific (Haniel 1915): Nautilus Wanneri Haniel, 1915, Kungurian, Timor; Endolobus (Solenocheilus) Brouweri Haniel, 1915, Kungurian, Timor. Remarks According to Shimansky (1967), Peripetoceras differs from Liroceras in having a less involute conch, a shallow ventral lobe and a slightly dorsally displaced siphuncle. However, these characters do not always allow a reliable separation; the box-shaped or inverted trapezoidal whorl profile in the adult stage can also be used as a further distinguishing criterion. It is not certain whether the Permian species also have a displaced siphuncle. Coelogasteroceras is similar to Peripetoceras, but differs mainly in the concave venter. Gordon (1965) and Shimansky (1967) considered Peripetoceras to be a very long-lived genus with a range from the late Early Carboniferous to the Late Permian. In fact, the Serpukhovian, Bashkirian and Moscovian species included in this genus are very similar to the Permian species, so it is a very conservative evolutionary line with little morphological change. In this respect, Peripetoceras would be comparable to Liroceras.