Abstract

The fossil cypriniform fish †Jianghanichthys hubeiensis from Eocene mudstones in Songzi, Hubei, China, was originally assigned to the extant cyprinid genus Osteochilus, then later to the new genus †Jianghanichthys by its original author, but with its familial status uncertain. Other authors subsequently assigned it to the cypriniform family Catostomidae. A detailed comparison of osteological characters shows that †Jianghanichthys is distinguished from all other cypriniforms by having (1) first principal anal fin ray branched; (2) supraorbital sensory canal largely exposed in frontal but roofed by longitudinal flange; (3) supraorbital sensory canal meeting the temporal sensory canal within the parietal; (4) maxilla bearing three dorsal processes; (5) dorsal surface of anterior end of dentary triangular and broad; and (6) the first centrum of †Jianghanichthys has a similar size and prominent posterior concavity to the second centrum. A computed tomography (CT) scan of a matrix-covered skull confirmed these unique characters, as well as that the pharyngeal teeth are either absent or not well formed. A series of phylogenetic analyses, using parsimony criteria and morphological characters, consistently recovers †Jianghanichthys in a polytomy with the non-loach cypriniform families, but it could not be placed within any recent family. Among osteological characters, few unique synapomorphies are shared by Jianghanichthys and recent families of Cypriniformes, whereas a large number of symplesiomorphies with the Catostomidae, Cyprinidae, and Gyrinocheilidae were found, indicating that Jianghanichthys is a stem taxon of Cypriniformes. Therefore, the first family of Cypriniformes known only from fossils, †Jianghanichthyidae, is erected to contain this Eocene cypriniform fish.