Unusual pharyngeal dentition in the African Chedrin fishes (Teleostei: Cyprinindae): Significance for phylogeny and character evolution

The dentition of cyprinid fishes is restricted to the right and left fifth ceratobranchials, which form the lower pharyngeal jaw (LPJ). The African members of the cyprinid subfamily Danioninae are nested within the tribe Chedrini. We compare the pharyngeal dentitions of African and of Asian Chedrini (Danioninae), including Danio rerio (Danionini), considering the following morphological characters: the pattern of dentition, the number of pharyngeal tooth rows, the curving and inclination of the tooth crowns, and the ratio of the tooth-bearing area to the length of the LPJ. Similar to a previous genetic based study a close relationship is proposed among the African genera Engraulicypris, Mesobola, and Rastrineobola, and among Leptocypris, Neobola, and Chelaethiops, all of which were formerly assigned as ‘Neobolines’. Species of Rastrineobola, Engraulicypris, Mesobola, and Neobola develop an additional (fourth) row of pharyngeal teeth. The dentition of Rastrineobola argentea (Pellegrin, 1904) and the shape of the LPJ of Engraulicypris sardella (Günther, 1868) characterize these two species as specialized within the Chedrini. An additional pharyngeal tooth row also occurs infrequently in the zebrafish D. rerio (Hamilton, 1822). The ‘fourth’ row of this fish species is possibly the result of a different process for acquiring four rows of pharyngeal teeth, likely by the splitting of one tooth row.