. Bulletin of the British Museum (Natural History). 92. 23 Figs 22, 23 Taphrodonta parallela Cooper, 1956, topotypes from Upper Pogonip Group (U. Llanvirn), 1 mile above entrance to Ikes Canyon, Toquima Range, Nevada, USA. Fig. 22, pedicle valve interior, the original of Cooper 1956: pi. 165, figs 7-11, USNM 117562g, x 4; Fig. 23, brachial valve interior, the original of Cooper 1956: pi. 165, figs 20-22, USNM 1175621, x 4. 165, figs 19, 22) there are two very small plates in the chilidial opening between the cardinal process and the interarea; these are not fused to the cardinal proc
. Bulletin of the British Museum (Natural History). 92. 23 Figs 22, 23 Taphrodonta parallela Cooper, 1956, topotypes from Upper Pogonip Group (U. Llanvirn), 1 mile above entrance to Ikes Canyon, Toquima Range, Nevada, USA. Fig. 22, pedicle valve interior, the original of Cooper 1956: pi. 165, figs 7-11, USNM 117562g, x 4; Fig. 23, brachial valve interior, the original of Cooper 1956: pi. 165, figs 20-22, USNM 1175621, x 4. 165, figs 19, 22) there are two very small plates in the chilidial opening between the cardinal process and the interarea; these are not fused to the cardinal process, and thus the cardinal process cannot be described as trifid. Species assigned Taphrodonta parallela Cooper, 1956: 741; pi. 165, figs 1-22 from Antelope Valley Limestone, Upper Pogonip Group (U. Llanvirn), Ikes Canyon, Nevada, USA. Species questionably assigned Taphrodonta bicornigera Nikitin, 1974: 58; pi. 5, figs 6-9 from Sarybidaik Formation (Llandeilo-Caradoc), right bank of Shiderty River, Narulgen, Kazakhstan, USSR (form of cardinal process uncertain from text and photographs). TAPHRODONTA (NANAMBONITES) Liu, 1976 1976 Nanambonites Liu: 145 Type SPECIES. Nanambonites paucus Liu, 1976. Diagnosis. Like Taphrodonta {Taphrodonta) but with chil- idium in brachial valve. Remarks. Nanambonites and Taphrodonta are the only two previously defined plectambonitacean genera with the two very small plates in the chilidial opening between the cardinal process and the interarea. The only difference we can find between them is the reported (but not illustrated) presence of a chilidium in Nanambonites, and this therefore merits their differentiation into separate subgenera. Liu (1976: 145) also mentioned the shape of the cardinal process and the shape of the double septum as generic differences, but the two taxa seem very similar to us in these respects. Species assigned Nanambonites paucus Liu, 1976: 146; pi. 2, figs 17-19 from lower formation of Jiacun Group (Llanvirn), Mount Jolmo
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