New Fish Assemblages from the Upper Devonian and Carboniferous of China and Mongolia

Diverse fish microremains have been found in the Upper Devonian and Carboniferous from Yunnan, Guizhou and Xinjiang provinces of China, and Baruunhuurai, and Shine Jinst areas of Mongolia. The Famennian Dazhaimen Formation of the Yudong I section (western Yunnan, Southwest China) contains the teeth of jalodontiform Jalodus australiensis (Long) and symmoriiform Stethacanthus sp., the symmoriiform buccopharyngeal denticles, scale of ctenacanthid type and actinopterygian teeth. The fishes of the Upper Tournaisian Yudong Formation of the Yudong II section, including the teeth of phoebodontiforms Thrinacodus ferox (Turner) and Thrinacodus sp.; symmoriiforms Denaea cf. fournieri Pruvost and Symmoriiformes indet., were found from the Scaliognathus anchoralis-Gnathodus pseudosemiglaber conodont Zone. A diverse fish assemblage including various chondrichthyans were recently described from the Carboniferous (Viséan-Gzhelian) of the Naqing, Narao, and Shanglong deep-water sections in Guizhou Province, South China (Ivanov and Hu, 2025). The symmoriiforms Denaea cf. williamsi Ginter and Hansen, D. sp., Stethacanthulus decorus(Ivanov), S. meccaensis (Williams), Stethacanthus sp., Symmoriiformes indet.; euselachian Gissarodus flabellatus Ivanov; Phoebodontiformes indet.; Jalodontiformes indet. were reported from these sections. Those findings are first reliable Carboniferous fish microremains from the deep-water deposits of China. A new assemblage including the the teeth of anachronistiform Cooleyella fordi (Duffin and Ward) and Cladodontomorphi indet., scale of euselachian type, and actinopterygian teeth occurs in the Moscovian Shiqiantan Formation of the Shuangjingzishuiqu section, eastern part of the Junggar Basin, Xinjiang, northwest China. This finding is a first record of anachronistiform shark in Asia. The fish material from Mongolia for this study comes from the Hushoot Shiveetiin gol section in Baruunhuurai area of south-western Mongolia, Indert-Uul and Tsagaankhaalga-2 sections from the Shine Jinst area, southern Mongolia. The Lower Famennian Samnuuruul Formation of the Hushoot Shiveetiin gol section contains the teeth of phoebodontiform Phoebodus sp. and jalodontiform Jalodus sp. from the glabra prima conodont Zone, the scale of ctenacanthid type from rhomboidea conodont Zone. The tooth of symmoriiform Denaea cf. fournieri was found in the UppermostFamennian Heermorit Member, Indert Formation (possible ultimus conodont Zone) of the Tsagaankhaalga-2 section. The chondrichthyan assemblage from the Lower Tournaisian Shombon Member, Indert Formation (kockeli-bransoni conodont interval) of same section includes the tooth of symmoriiform Denaea cf. fournieri and hybodontid type scale. The tooth of phoebodontiform Thrinacodus ferox occurs in theUppermostFamennian Heermorit Member, Indert Formation (possible ultimus conodont Zone) of the Indert-Uul section. The Lower Tournaisian Shombon Member, Indert Formation of the same section contains the tooth of symmoriiform Stethacanthus sp. from the Protognathoduskockeli to the Siphonodellabransoni conodont zones; the teeth of squatinactiforms Squatinactis caudispinatus Lund and Zangerl and Squatinactis sp. from the Si. duplicata conodont Zone; and the teeth of symmoriiform Denaea cf. fournieri and Cladodontomorphi indet. from the Si. sandbergi conodont Zone. These findings are the first records of Carboniferous fishes in Mongolia.